Blue balls?

I'd say it doesn't take that long. It can happen fairly fast depending on the sexual activity that's causing it. Like if a girl is teasing him good and keeps it up, (this doesn't have to include rubbing!) after he has had a boner for, let's say 15 minutes, if she suddenly stops and then walks off, he'll be left with a huge urge to get off. But if he's where he can't do anything to relieve himself, he'll start getting soft andbe left with this feeling like a numb leg that was asleep and now waking - a weird prickly feeling and precum that's made his pants wet. When you suddenly leave a guy like that after having teased him hard for awhile you'll have blue balled him. Maybe some guys will have needed some teasing by rubbing first, and depending on how good the girl was as teasing, then when the girl suddenly stops and leaves him in that situation, she'll have left him blue balled.

It can take a while. All depends on the level of sexual activity, really. Like if you're rubbing him or teasing him for a while he will get blue balls. A simple erection, however, won't cause anything.

It depends, but normally it should take a while of long sexual stimulation. All the guy has to do is ejaculate and it solves the problem. I have masturbated for hours and sometimes I get it and sometimes I don't. I have had a real bad case when there was severe pain.

The one time I've had blue balls was when I was with a woman for an evening. It took about 4-6 hours of playing without ejaculating (i.e. I had an erection for that entire period of time without releasing through ejaculation). It is apparently caused by the pooling of fluids including blood in the testes. The blood becomes oxygen deprived (hence the blue). The excess fluid and I believe muscle constriction over the period of time means that it hurts. For me it only hurt for the morning. By noon I was back up and running.