Leave the d*mn PCs on!
I always encourage my clients to leave their PCs turned on, for several reasons.
1. Leaving them on means that they run at a more-or-less constant temperature, which is much better for component life. Many SOHO PCs are in outbuildings which are unheated during the night. This can lead to condensation and subsequent corrosion problems as the temperature drops.
2. Windows updates are scheduled by default to happen at 03:00, when the users aren't there to be interrupted or inconvenienced by them. Anti-virus updates and scheduled scans also run during the night.
3. I operate remote support via VPN link from my office. This often means remote accessing a PC out-of-hours.