I occasionally can have two orgasms with one erection, but the conditions must be just right. First, I probably have not had sex or jerked off for a couple days, so I have some build up, and extra sensitivity. Second, my partner is probably fairly tight, or gives me oral first. And last, if I really want to maintain the erection, and I am not getting oral first, I probably will not cum inside of her so there is no extra fluid in there.
On the other hand, I find that if my girlfriend is really horny, she can find a way to keep me stimulated orally after we have sex.
My conversations with other guys suggests to me that most are not able to keep an erection. But, I think it is because most guys are too lazy to try and keep it up. They are just one and done. I would venture to guess that most of the guys in this forum are actually NOT that way since we all seem to have a pretty strong interest in sex!
GOTTABHUGE!