Some folks like to keep their machine powerd up all the time (usually with energy-saving features enabled.) They claim this saves wear-and-tear, as avoiding a power cycle is a good thing.
Others only power up their systems when they want to use them. They claim this does the same thing, as it’s only on 1/3 to 1/5 of the time as the other 'puter.
I was going to make this a GQ, but after a brief search, it seems the jury is still out.
I’m with the folks leaving it on all of the time, if only for the SETI@home good feeling I get
Moderator’s Note: Since that other COSR thread has gone off on some tangent about URL’s, I think I’ll just go ahead and move this one over to COSR (even if it didn’t technically start out as a Comment on a Staff Report).