>How often do you restart your computer?
Every single time.
Whenever I think there's a possibility that the need to reboot has not been overcome since the DOS days and W9x.
I find many more unexpected needs to restart in Windows NT6.
Unless your PC is miserably encumbered, it only takes a few seconds to reboot or cold start, so why hesitate.
Reboot early and often.
>I'm old enough to remember the times when computers were restarted regularly
During those same times I remember other operators who never wanted to turn off their computers for any reason, almost acting like they were mainframes and afraid they might not boot back up.
Looking at the answers, here's my anecdata: I usually only turn one on when I'm really working on it, and completely power down when finished.
Never hibernate or sleep, why bother?
OTOH the ones I had at work hooked up to scientific instruments never get turned off for years, except for power failures in excess of battery backup time. Once I got IT out of the lab it was possible to craft Windows XP for far more reliability than they had dreamed about, or achieved since on their office machines with NT6.