I try to always get into my stand 1 hour before sun-up. Legal shooting time in Missouri starts 30 min before sun-up so that gives me 30 min to get situated and as silent as I can.
Coming out, I usually come out right when shooting light has faded and I can't see through my sights whether rifle or bow. Now, I do this as quietly as I can and I make sure there are no deer around before I exit. But I don't wait until it's completely dark.