Well, 5 minutes is when I'm at work, where there is the thrill that someone might hear or see me doing it (there is a bit of space between the door of the stall and its frame, and I'm always afraid someone might see my legs moving while jerking) and I'm not holding back. I can last a lot longer at home by edging.
Edging is also called the stop-and-method. You masturbate until you feel yourself coming close to an orgasm and then you stop or slow down your rythm until the rush dies down, and then you start again. You can last for hours like that (I can do it for over 2 hours, but by then I start getting blue balls and it is so painful I have a hard time even maintaining an erection so I don't recommend it for that long) and your orgasm are much stronger. As a nice bonus, you get to know your limits and control your stimulation a lot more which I'm sure is quite helpful in not going too quick and blowing off your load prematurely while have sex with someone else.