For me it's not the main reason, an important part of it, an expectation, but not the main reason.

And my point is the guys in those (often) can go almost non-stop for very long periods of time with super hot women (some of them) where even watching it I can't go as long as they can, and they're actually with the woman/women.

Maybe Black is one of those gifted individuals. And any straight man would eventually be able to finish when doing it with the hottest of porn stars, especially if it's with two of them at once... if not than he's not human or maybe dead.