When I was a wee teenager, I occasionally did the super-fast-stroke-off, either to see how fast I could do it, or out of necessity. Even then, though, I wasn't a fast cummer. If anything, I've got the opposite of premature ejaculation. Unless I just bear down and focus on cumming as fast as I absolutely can, I will go for at least 5 minutes. And usually a good bit longer (like 40 minutes).
And besides, as others have said, that's really no fun. I like to relax and enjoy it. Get into a slow rhythm. Make it last awhile.