One thing to add to this discussion is that many mature bucks will remain IN cover for safety. The younger guys possiblyhaven't developed the cover = safety sense yet.

And as someone mentioned earlier nocturnalism also adds to this. Big boys have learned that there is less hunting pressure/predators in deeper cover, and come out of it later in the evening when predators are less numerous. If the younger boys survivea season or twothey will start to gain the intelligence to gauge hunting pressure, and how cover equates to safety.