I don't think my case is typical, but maybe it can help establishing a boundary.
After years of updates and a lot of install/uninstalls, I have around 14GB for my Ubuntu system. And 13GB of snaps. And 2GB of flatpaks. And a lot of nonsense I should delete but I really don't have real motivation to; system is darn fast anyway. And I have a 100GB home which is a way better target for clean up when the disk gets full.
Next LTS might be a total reinstall. Much easier than clearing that mess. Or maybe not. We'll see.