In my experiance, the height is dictated by situation and location. As alrady said cover is a big one. If you are planning on harvesting an animal in hardwoods standing 20 yards, then you likely should be in the 18' range. If you can get in a tree with more cover and plan your situation to harvest that animal at 15 yards then 12' will work. Here in central illinois I have climbed to 18' and took game, and then stood 8-10' in a Hedgetree and had deer feed right under me. This taught me that in a tree with alot of cover don't have to be higher, but shot's are much more limited. I Believe that hunting from a lower height will force you to be a better hunter, so you up for the challenge?