Originally Posted by Amuro
According to the follwing, CPU's failure increase is a direct function of the number of thermal cycles and the change in temperature above ambient. So in addition to heat, turning the computer on and off also reduces CPU life.
Yup, turn it off, the silicon gets cold and contracts. Turn it on, the silicon gets warm and expands, and this causes the silicon to fatigue, eventually. This is why I was always in the "Leave it On" camp, but man, I just let my computer go into standby mode after an hour anyway because I don't like paying the electric bill.