years.
I've been going through my oldest machine, nexus.zyp.org, package-by-package, in an effort to reduce cruft and clear out some of the old junk that is no longer used, or has been superceded by newer versions.
So far today, I've managed to remove almost 400MB of stuff. I'm hoping to be able to remove at least that much more, before I'm finished.
Which reminds me. . . although most of the stuff I've been able to remove has been found via manual walking of the installed packages list, anyone running Debian should take a look at
deborphan. It's a very useful utility for removing cruft. Another useful, if slightly less so, utility in Debian is cruft, named after what it helps you remove.