jmad

Depending on the situation, I usually need at least 15 minutes of non-stop intercourse to blow my load. However, if I wear a condom I can go for over an hour without down time. My girl has never complained about soreness even when we have sex on and off for hours at a time. Although I have never worn a stopwatch during sex, I think 15-20 minute blocks of sex are the way to go. Throw in nap/foreplay breaks, rinse and repeat.

Edit: I forgot to mention that I'm studying abroad right now, so I party like 5 times a week, and only have sex about once a week. This is probably why I can have sex for indefinate periods of time without any irritation to my knob.

Doing the math, if you have sex for an average of 30 minutes each session, at 5 sessions a week, you're having more sex than me, which could be why people get irritation after a short time of intercourse(15 mins or so).