Actually, what TLM is describing is familiar to me -- and not what I associate with what's being taught in the book, The Multiorgasmic Man. I've read the book and that's different from what I experience.
It has nothing to do with exercises, and it is not orgasming without ejaculating in order to continue. It's wholly an internal, natural thing. I shoot once, and stay hard and I can continue to jack and shoot another load approximately every 30-60 seconds. It's pretty standard that I shoot 4 or 5 loads consecutively. I do remember the most I'd orgasmed in one session was in college with 12 loads in 30 minutes, from the first to the last, not including the warm up

I had to stop because my dick was beginning to hurt. And yes, while the volume tends to diminish, the intesity, for me, does not. Ocassionally, maybe around the 5th or 6th load, I'll actually shoot more forcefully and with more volume than the first. It's almost like I *have* to continue, or I haven't really been satisfied. I always get comments, and I just tell them they got into the sideshow without a covercharge LOL
On the other hand, a guy once told me that it's really not multiple orgasms. He claimed that men simply aren't capable, and what I experience is one very long drawn out orgasm. I'm not certain that's true either, as there's a distinct break for me between each.