tried this myself tonight, but i have done it many times, but never timed myself. what i usually do is take my practice shots, usually between 20-30, and then i take my last shot and try to hold it for an extended period of time, somewhere over a minute. I have never actually timed myself before, but tonight i timed myself and could hold it for about 1 min. and 30-40 seconds before i felt that i should take a shot. I am pulling 82lbs, with 65% letoff. I did it twice in a row, with about the same results, so im pretty sure about 2 minutes would be my limit.