Hello
I also hunted for years at around 15 foot. Lately I almost always use a climber and will go as high as the tree allows or my thirty foot retrieve strap comes to its end. Sometimes of course, my height is dictated by surrounding branches, obstacles that block good shooting lanes. Usually I'd say I'm 25-30 feet up.
End result, the higher the better, its easier to stay unnoticed. The shooting angle makes the shot a little more difficult, but a little practice helps tame that problem.

Dan