First off shrew I sure hope your not planing on taking any 65 yard shots!! Give yourself a little time, like a few years.
As far as random unmarked distances I know a whole bunch of guys who have trouble with that. I have the kids toss plastic pop bottles or beer cansanywhere they want and then I try the shot with grassgrabbers/judo points. I shoot at them from a tree stand but at ground level. The kids are cruel and throw my targets behind the tree, under my feet, between trees ect. Thats when the ability to shoot unknown distances really comes into play.
There may be a few who can make 9 out of 10 65 yard shots, but not many at least not in a hunting scenario. It does sound like your ready for the woods, just let them get close and good luck bud.