>> My take is to purge old libs after every new release. Once, I had to do >> it in the middle of a version upgrade, because there was no space left >> on disk to complete it. My fault only, I had a very tight custom >> partitioning layout. > > I don't think it's that easy. One case it comes to mind it's that > there's a short window after an update and between `pkg_add -u` where > you're running a new system but with old ports. Your entire system > (except base stuff) would break if you remove the libraries. There may > be more edge cases like this.
If you use packages rather than self-built software from outside of ports/packages, sysclean already takes care of this when suggesting what to remove.