OK fine, here are some details. When I was 19 I could get an erection, have sex, ejaculate and continue to maintain the erection post-ejaculation so that I could continue intercourse until I was able to ejaculate a second time. I did, on at least one occasion try to keep it up until a third climax was reached, but I hurt my back shortly after my second. Ah, youth.
Ten years and 50 lbs later/heavier I usually have sex once a day. Having sex twice in the same "session" is pretty much a thing of the past. However, I'm usually capable of having sex again in about an hour. Now on the rare occasion I try for three times in one day the third climax results not in the expected traditional white goo, but a completely clear fluid. It would seem that my balls do not like being forced into overtime and are just trying to shut me up by throwing a wad of precum out the pipes in the hopes they'll get some rest before they have to start producing more sperm.
Now I'm reasonably certain that the underlying factor behind all of this is the buckets of growth hormones and testosterone that naturally drop after puberty. When I was 15 i could jack-off 5 times a day, every day. One of these days I'm going to experiment with testosterone injections and try having a real good 4-day weekend.
Of course there is a psychological component also.
1. In highschool I was surrounded by 500+ women all the time
2. Studied show that men who live/work in groups have a higher testosterone count than men who do not. In school we had gymclass and cliches. In adult life we do not.
3. Listening to the song "My ****" by Mickey Avalon about 5 times in a row at a loud volume level pumps me up psychologically to a point where I'm fairly certain I could **** anything that moves.