I like about 12ft to 20 ft although sometimes a little higher or lower is what you need.I have seen 30ft but I got a nose bleed and the tree was blowing in the breeze like a mast on a sailboat.
At most of the places I sit if I go much higher than 15ft I am really cutting down on my shooting lanes. I guess it just depends on where you hunt.

Just remember that at 3ft or 30ftyah gotta strap yourself in!!!!