Regards
This. I've always kept my machine on even before discovering bitcoins. I typically ran various distributed networking projects such as folding@home, distributed.net, etc. Plus I'm a pretty avid gamer and will always have top-of-the-line (or a few months old) vid cards and might as well have them contribute to mining. I may stop them once they become the equivalent of crappier CPUs (that is, only contributing like .5% or worse of my total hashing power). But I'll only do that to quiet down my man-cave and make my place of Zen again
Or if I can figure out how to use the wasted heat from the cards to heat my fish tank, I'll keep 'em going and turn off my tank heaters (since my PC is on a UPS and my fish tank heaters aren't)