Yea I had sex like 3-4 times before I could ever cum. I'd go for over an hour and not even come close. I used to wack off so much that I got so used to it that nothin else would work. I quit masturbatin so much and I was finally able to cum. It was real frustrating.
Well all I can say is that sometimes if I know I am going to have sex I will beat off a few hours before I go out with a girl or a couple times that day before I go out and when I end up having sex I usually go way over normal time, alot of the time over an hour. But I think it helps with stamina because it sort of makes your penis less sensitive and a little tired but not to the point that you can't get a hard on and plus ever since I have been doing Penis Enlargementing my erections are always rock hard no matter how many time I beat off or have sex in a day!!!! This is just my point of view on it!
I think the more often you masturbate the, more sorta "expected" it becomes and it becomes like a general chore which i think in turn makes sex last longer becuase its being done so often. In other words pretty much what Bigd5903 said.