If you can't sit all day, at least try to sit an hour longer than the hunters around you. Deer quickly pattern other hunters, and when everyone else heads back in at 10am they may bump a deer your way. Deer aren't on a set schedule, especially during the rut, so you never know when you'll see one.
One thing I have learned about morning hunts, however, is that it's better to arrive a little early than late. Nothing is worse than trying to rush to the stand in attempt to beat the rising sun. Whenever that happens, I invariably seem to kick a deer off my stand. If you get there in the dark, you can get away with more movement in getting set up.