When masturbating no longer yields any fluid. You have masturbated all that you can: you have reached your fapping capacity. Your fapacity.
I was at it all day, it took 6 tries before I reached my fapacity.
The amount of times one can fap in a 24 hour period.
My fapacity is about 6 on a good day.
The capacity at which one can fap. The quota; the limit of fapping. The point of male masturbation when one is about to nut.
Derek was really going at it, until he reached his fapacity.