Shooting offhand is a difficult skill to master (or at least for me it is).

Personally I think you should be able to put 10 out of 10 shots in the black from whatever distance and whatever position you are shooting from.

If given the choice I always take a rest even if I'm in close. Usually the only times I need to shoot offhand is when I jump an animal at 10 or 20 yards....in which case I am pretty accurate.