However long it takes you to ejaculate. It differs with each male due to the PC muscle strength. I forget what PC stands for, but it is the muscle that contracts around the urethra and vas deferens that prevents semen from going through. It contracts earlier if weaker, and thus some men can't last as long as others, but there are ways of strengthening the muscle if you are willing to devote of a lot of time and practice to the exercises.
