I use these metrics for my own infrastructure as well and find them to be quite useful.
pacnew you will know, when you need to upgrade a config file. I didn't add an alert yet because I thought that maybe
a lot of files will have accumulated.
orphans is useful in case a PKGBUILD gets updated and a dependency moved to
optdepends. That case could theoretically break
a playbook when deploying a new machine.