The best way to keep going is to have an orgasm without ejaculating. You can then go all night long and when you do ejaculate it will be more powerful than if you ejaculate with your first orgasm. BTW, in case you didn't know orgasm and ejaculation are two different things. You have an orgasm with you ejaculate, but you can have orgasm without ejaculating.
Don't stop! Don't you ever stop till you both drop! Serious. At least over an hour is the minimum. But realistically, nothing more than 3 to 4 hours. You can't have sex all the time, every time so make the most of it.
Oh young buck, k let me let you in on a little secret, go as many times as it takes for her. End of question never ever leave her hanging, girls want a guy who can give them what they need don't get yours and leave her just strap up and be a MAN and finish the job