I use a 26 foot retractable dog leash and hang it on my foot platform. When it stops letting out line I stop climbing. If I can't get at least 20 foot or so off the ground I most likely won't climb that tree unless it is my only choice. I'd rather make a longer shot by a few yards than be sitting close to the ground.

Remember that deer are use to the tops of trees moving around but the trunks shouldn't move at all.