I used to be like Steve, If I wasn't at least 25 ft, then I felt "naked". I'd go as high as 30-35. But the last few years, I have learned to hunt on the "backside" of the tree keeping the tree between me and where the deer come from/ where I anticipate them to be. The only downfall is that I stand up 90% of the time. Since I have started using this type of set up, I'll rarely go over 25 ft, but still like to get up to at least 20, I feel this helps your scent "stay high" in your immediate hunting area.
Oldhat