I just purchased my second Mac (new Mac mini) and bought a WD 1TB external hard drive to go with it. I have it constantly plugged in to my mac mini on my desk, and will rarely ever move it. My question is, should I leave my external hard drive on all day long, or should I turn it off unless I'm backing something up? I have time machine set to back up every few hours, and was wondering what everyone else does? I believe that when my mini goes to sleep, the external hard drive does to, as I hear the disk start up on the external hard drive when I wake the mini. Will it harm the hard drive? Thanks!