How can an administrator determine the documents to which a collaborator collaborates before deciding to remove the guest license from that user?

I.e. In the near future I foresee that we will reach the top limit of 20 guest license users and I will have to remove a few. However, I can't really identify the best candidates for removal since I can't know (as far as I can tell) when they were added or what documents they were collaborating to (and incidentally the status of such documents).

The only 2 "bad" options I've considered are as follows:
delete the user and transfer the accesses to me, then I'll know what they were (I assume). A bit aggressive an approach I'm afraid, especially if accesses were still required.
ask the users to go check the "shared with me" section and report to me the contents. A bit uncomfortable an approach I'm afraid, especially if the collaborator is a client.

Similarly with standard licenses it would help to see the latest contributions of a given user to evaluate how active they are. And why not maybe sort users by their amount of activity, for licenses management purposes? I know the dashboard has a similar activity scoreboard but for "most closed documents" or something like that.

Final thoughts: for each license / user it would be helpful to see the date they were added to the platform and by who they were invited (if they were invited).

Note that my point of view is admin; I've read about what an account owner sees in the billing section and so far I think my comments remain relevant, but I may have missed something.