Nothing alters a whitetail's feeding cycle like human activity. To gauge how early you need to be on stand, consider the remoteness of your chosen field. The more remote, the earlier deer will be up on their feet in daylight. Of course, it's always best to hedge your bets and arrive on stand much earlier than needed. When hunting fields closer to lots of activity (well-used roadways, for instance) count on deer to linger in "staging areas" just off the fields until the last possible light. It can be hard to give up on a hot field, but haunting the ingress/egress corridors of a staging area packed with plenty of fresh rubs might well be worth it.