Changing the default user package library

[jcblum]

You can definitely set up one or more user libraries for regular R installations and it has historically not been uncommon to do so (the R Installation and Administration guide pretty much assumes you will: R Installation and Administration). There was a bit of discussion of the downside of having a single version-independent user library (along with other approaches to easing R upgrades) in this thread:

Reinstalling packages on new version of R

Be careful. This will update all the packages in this shared library location, which is perfect if you're only running R-3.5.0, but may cause problems if you ever want to run code on older versions of R. If you're the only user, and this is not production code, this practise is probably fine. But if you are running code in a shared environment, or a production environment, then do make sure you follow robust practise when updating R versions.