All the time...

because I use Time Machine.... BUT.... I have 3 other external Hard Drives that I also leave on at all times, (or nearly so)... and they are fine. It's when they are NAS that I have the problems. I don't understand it because I'm sure they use the same hardware in them, same drives that is? I'm wondering if it's the NAS configuration on the drives more than the hardware itself. - JamesJM