diff --git a/DESCRIPTION b/DESCRIPTION
index d3f157d..851f2ec 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -3,8 +3,8 @@ Type: Package
 Title: Informative Messages About Outdated Packages
 Version: 0.1.0
 Authors@R: person("Jacob", "Scott", email = "jscott2718@gmail.com", role = c("aut", "cre"))
-Description: When a package is loaded, the source repository is checked for 
-    new versions and a message is shown in the console indicating whether the 
+Description: When a package is loaded, the source repository is checked for
+    new versions and a message is shown in the console indicating whether the
     package is out of date.
 License: MIT + file LICENSE
 Encoding: UTF-8
diff --git a/R/available_version.R b/R/available_version.R
index a857b2e..8f9c5aa 100644
--- a/R/available_version.R
+++ b/R/available_version.R
@@ -123,8 +123,8 @@ available_version_impl_repo <- function(pkg, repo = NULL, repo_alias = NULL) {
       sub(x = _, "/R/.+$", "") |>
       sub(x = _, "/src/contrib$", "")
 
-    repo_alias <- names(repos_option)[grepl(pattern, repos_option, fixed = TRUE)]
-    if (length(repo_alias) == 0L || identical(repo_alias, ""))
+    repo_alias <- names(repos_option)[grepl(pattern, repos_option, fixed = TRUE)][1]
+    if (is.null(repo_alias) || any(is.na(repo_alias)) || identical(repo_alias, ""))
       repo_alias <- repo
   }
 
diff --git a/R/updateme_on.R b/R/updateme_on.R
index 93c325b..23b7356 100644
--- a/R/updateme_on.R
+++ b/R/updateme_on.R
@@ -3,27 +3,20 @@
 #' These functions may be useful if you find the slight delay caused by
 #' updateme looking up new package versions to be slowing down your workflow.
 #'
-#' @return `NULL`, invisibly
+#' @return The old `updateme.on` option, as returned by `options()`
 #' @export
 #'
 #' @seealso [updateme_sources_set()] to turn updateme off for individual
 #'   packages
 #'
-#' @examples
-#' if (FALSE) {
-#'   updateme_off()
-#'   updateme_on()
-#' }
 updateme_on <- function() {
   options(updateme.on = TRUE)
-  invisible(NULL)
 }
 
 #' @rdname updateme_on
 #' @export
 updateme_off <- function() {
   options(updateme.on = FALSE)
-  invisible(NULL)
 }
 
 updateme_is_on <- function() {
diff --git a/R/updateme_sources_set.R b/R/updateme_sources_set.R
index 6d5d5ed..8a84f47 100644
--- a/R/updateme_sources_set.R
+++ b/R/updateme_sources_set.R
@@ -52,37 +52,38 @@
 #'   packages
 #'
 #' @examples
-#' if (FALSE) {
-#'
-#'   # If you want to check non-standard repos for new versions of packages,
-#'   # you'll first have to set the repos global option. Note that each
-#'   # option must be named for compatibility with updateme
-#'   options(repos = c(
-#'
-#'     # Your default repos, e.g. c(CRAN = "https://cloud.r-project.org")
-#'     getOption("repos"),
-#'
-#'     # The tidyverse r-universe, including dev versions of tidyverse packages
-#'     tidyverse = "https://tidyverse.r-universe.dev",
-#'
-#'     # The r-lib r-universe, including dev versions of infrastructure packages
-#'     # like {cli}, {rlang}, etc
-#'     rlib = "https://r-lib.r-universe.dev"
-#'   ))
-#'
-#'   # 1. New versions will first be looked up in the tidyverse r-universe
-#'   # 2. If not found, they will be looked up from your usual CRAN mirror
-#'   # 3. {bslib} will always be first looked up from GitHub
-#'   # 4. {cli} will always be first looked up from the r-lib r-universe
-#'   updateme_sources_set(
-#'     "tidyverse",
-#'     "CRAN",
-#'     bslib = "https://github.com/rstudio/bslib", # Name is optional here
-#'     cli = "rlib"
-#'   )
+#' # If you want to check non-standard repos for new versions of packages,
+#' # you'll first have to set the repos global option. Note that each
+#' # option must be named for compatibility with updateme
+#' old_repos <- options(repos = c(
+#'
+#'   # Your default CRAN mirror will likely be something like this
+#'   CRAN = "https://cloud.r-project.org",
+#'
+#'   # The r-lib r-universe, including dev versions of infrastructure packages
+#'   # like cli, rlang, etc
+#'   `r-lib` = "https://r-lib.r-universe.dev"
+#' ))
+#'
+#' # 1. New versions will first be looked up from the r-lib R universe by default
+#' # 2. If not found, they will be looked up from the usual CRAN mirror
+#' # 3. dplyr will always be first looked up from GitHub
+#' # 4. ggplot2 won't be looked up or notified about
+#' old_updateme_sources <- updateme_sources_set(
+#'   "r-lib",
+#'   "CRAN",
+#'   dplyr = "https://github.com/tidyverse/dplyr", # Name is optional here
+#'   ggplot2 = NA
+#' )
+#'
+#' # memoise should now be looked up from the r-lib r-universe
+#' if (interactive()) {
+#'   library(memoise)
 #' }
 #'
-# TODO: Add .append arg?
+#' # Restore old options
+#' options(old_repos)
+#' options(old_updateme_sources)
 updateme_sources_set <- function(...) {
   options(updateme.sources = updateme_sources_set_impl(...))
 }
@@ -119,17 +120,17 @@ updateme_sources_validate <- function(src, pkg = NULL, throw = cli::cli_abort) {
 
   handle_no_sources <- function() {
     if (!is.null(throw)) {
-      repos <- names(getOption("repos"))
+      repos <- cli::cli_vec(names(getOption("repos")), style = list("vec-last" = " or "))
       throw(call = caller_call(6), c(
         "Invalid package source {.val {src}}.",
-        "i" = "Package sources must be either:",
-        " " = '1. One of {.code names(getOption("repos"))}',
-        " " = "2. {.val bioc} to check te version on Bioconductor",
-        " " = "3. {.val github}/{.val gitlab} to check the version on GitHub/GitLab if possible",
-        " " = "4. The URL of a specific GitHub repository, e.g. {.url https://github.com/wurli/updateme}",
-        " " = "5. The URL of a specific GitLab repository, e.g. {.url https://gitlab.com/r-packages/yum}",
-        " " = "6. {.val NA} to turn {.pkg updateme} off for a package",
-        " " = "7. {.val NULL} to return to the default behaviour"
+        "i" = "Inputs must be:",
+        " " = '- One of {.code names(getOption("repos"))}, i.e. {.val {repos}}',
+        " " = "- {.val bioc} to check the version on Bioconductor",
+        " " = "- {.val github}/{.val gitlab} to check the version on GitHub/GitLab if possible",
+        " " = "- The URL of a specific GitHub repository, e.g. {.val https://github.com/wurli/updateme}",
+        " " = "- The URL of a specific GitLab repository, e.g. {.val https://gitlab.com/r-packages/yum}",
+        " " = "- {.val NA} to turn {.pkg updateme} off for a package",
+        " " = "- {.val NULL} to return to the default behaviour"
       ))
     }
     NULL
diff --git a/R/zzz.R b/R/zzz.R
index aec8c67..8fa238f 100644
--- a/R/zzz.R
+++ b/R/zzz.R
@@ -5,6 +5,9 @@
     max_age = 60 * getOption("updateme.cache_expiry", 60)
   )
 
+  # Note: <<- does not modify the global environment, it simply memoises
+  # existing functions included in this package. This is the approach
+  # recommended by the {memoise} package itself - see ?memoise::memoise
   available_packages <<- memoise::memoise(
     available_packages, cache = updateme_cache
   )
diff --git a/man/updateme_on.Rd b/man/updateme_on.Rd
index b6428ae..a7816e6 100644
--- a/man/updateme_on.Rd
+++ b/man/updateme_on.Rd
@@ -10,18 +10,12 @@ updateme_on()
 updateme_off()
 }
 \value{
-\code{NULL}, invisibly
+The old \code{updateme.on} option, as returned by \code{options()}
 }
 \description{
 These functions may be useful if you find the slight delay caused by
 updateme looking up new package versions to be slowing down your workflow.
 }
-\examples{
-if (FALSE) {
-  updateme_off()
-  updateme_on()
-}
-}
 \seealso{
 \code{\link[=updateme_sources_set]{updateme_sources_set()}} to turn updateme off for individual
 packages
diff --git a/man/updateme_sources_set.Rd b/man/updateme_sources_set.Rd
index e4464aa..408f63a 100644
--- a/man/updateme_sources_set.Rd
+++ b/man/updateme_sources_set.Rd
@@ -59,36 +59,38 @@ to configure a personal access token (PAT):
 }
 
 \examples{
-if (FALSE) {
+# If you want to check non-standard repos for new versions of packages,
+# you'll first have to set the repos global option. Note that each
+# option must be named for compatibility with updateme
+old_repos <- options(repos = c(
 
-  # If you want to check non-standard repos for new versions of packages,
-  # you'll first have to set the repos global option. Note that each
-  # option must be named for compatibility with updateme
-  options(repos = c(
+  # Your default CRAN mirror will likely be something like this
+  CRAN = "https://cloud.r-project.org",
 
-    # Your default repos, e.g. c(CRAN = "https://cloud.r-project.org")
-    getOption("repos"),
+  # The r-lib r-universe, including dev versions of infrastructure packages
+  # like cli, rlang, etc
+  `r-lib` = "https://r-lib.r-universe.dev"
+))
 
-    # The tidyverse r-universe, including dev versions of tidyverse packages
-    tidyverse = "https://tidyverse.r-universe.dev",
+# 1. New versions will first be looked up from the r-lib R universe by default
+# 2. If not found, they will be looked up from the usual CRAN mirror
+# 3. dplyr will always be first looked up from GitHub
+# 4. ggplot2 won't be looked up or notified about
+old_updateme_sources <- updateme_sources_set(
+  "r-lib",
+  "CRAN",
+  dplyr = "https://github.com/tidyverse/dplyr", # Name is optional here
+  ggplot2 = NA
+)
 
-    # The r-lib r-universe, including dev versions of infrastructure packages
-    # like {cli}, {rlang}, etc
-    rlib = "https://r-lib.r-universe.dev"
-  ))
-
-  # 1. New versions will first be looked up in the tidyverse r-universe
-  # 2. If not found, they will be looked up from your usual CRAN mirror
-  # 3. {bslib} will always be first looked up from GitHub
-  # 4. {cli} will always be first looked up from the r-lib r-universe
-  updateme_sources_set(
-    "tidyverse",
-    "CRAN",
-    bslib = "https://github.com/rstudio/bslib", # Name is optional here
-    cli = "rlib"
-  )
+# memoise should now be looked up from the r-lib r-universe
+if (interactive()) {
+  library(memoise)
 }
 
+# Restore old options
+options(old_repos)
+options(old_updateme_sources)
 }
 \seealso{
 \code{\link[=updateme_on]{updateme_on()}} and \code{\link[=updateme_off]{updateme_off()}} to disable updateme for all