I've always turn mine off when I'm sleeping or not at home. I don't see the point in leaving it running 24/7 if its not doing anything. If you want another reason, it could save your house from burning down. I left mine running once when I just popped out for a few minutes. Those few minutes turned into a couple of hours. I got home, threw my keys on the desk went to the kitchen and came back to see my computer bellowing smoke and flames out the PSU. If I had stayed out 5 or 10 more minutes I may not have had a house to come home to.