I've taught and wrote books for men around tantric sex for over a decade now. My most crowded workshops are multiple orgasm training for men. And therefore personally I've practiced for years what I preach. Anything under two or three hours of sex is a wasted time in my opinion. I've gone as long as eight to ten hours, taking short breaks for snacks showers, run an errand. Native tribes have sex rituals that last for days, those are beautiful.
Alas it is hard to find a man or woman who is this psychically strong. Most homo men try to force an ejaculation out of you like that's the accomplishment or there are cookies burning in the oven.