When I select "Sleep" my Mac mini goes to sleep just fine, with the power lite pulsating. When waking up, it jumps to life in less than a second. However, if left in "Sleeping" mode for a period of time, say, two or three hours, the pulsating lite goes off altogether. Waking the mini appears to take somewhat longer, but, wakes up just the same. It would appear that my new Mac mini is Hibernating after a sleeping for a while, just like my Dell laptop does if not "woken up" after a while. Is there a setting for this somewhere that I can't find in Preferences, or is this just a normal 'fixed' factory setting?