I have a vista sp2 install from 2006 that's still working fine. Been in use every day since it was installed as well. I, or the person who regularly uses it, haven't installed much or anything new in the past few years, mostly just games through steam if anything. Most of its software was a month-one install from 2006 that have all been working since then (aside from antivirus/firewall changes/upgrades). It's usually used with VMs, work, games, movies, and to print/scan/etc. I have not had to reinstall it since 2006 and it has not really dropped in performance since then either. Still boots relatively quick, fully updated, no trouble. It's way past time to build a new one of course, but I don't think I'll ever have to mess with that box until its hardware starts to fail (which might actually start to happen soon; an 8 year old cheap NAS hdd of mine recently failed; was on 24/7).
Stick to stable drivers, not bleeding edge, and you won't hose your system so quick, but that's only a problem if you're constantly playing the newest games. Think with that vista box I only upgraded the vid drivers 4 times over its lifetime, and never touched any of its other drivers from day-one. Dusty as hell though lol, really should clean it.