We all love a good night's sleep.  But I think adequate rest is a more important factor for decision making in the hills than many people give it credit.  The human body has been conditioned to sleep at night and be active during the day.  Therefore it's more natural to be at the top of the mountain in the afternoon/ evening than first thing in the morning.  And it goes without saying, but it's more aesthetic to ski lines in the sunshine than in the shade (there are always exceptions to that basic idea though :).   A well rested skier is a skier that's stronger physically and sharper mentally.  We often hear and read stories of sleep deprived alpinists, on the move for 24 hrs or more.  What you don't often hear about are stories of poor decisions that folks have made, directly as a result of mental fatigue.  I personally have been avalanched because I made a poor decision, in large part due to lack of sleep.  Now I am more aware of the cobweb influence there.  Where route finding decisions and safety lie in a delicate balance, the importance of sleep/ rest should not be taken lightly.