An Asian girlfriend taught me how to have multiple orgasms without losing my erection between each orgasm. I was 31 and in very good shape. Basically the technique is to fuck with full strokes until I almost have an orgasm. At a certain point in the buildup to the orgasm, I had to slow my stroking in her pussy or ass. Then, I would have an orgasm and cum, but half my normal volume. We practiced for a while until I could recognize the slow-down point and how slow to go. After orgasming, I would wait about 30 seconds and resume normal fucking, full strokes. The most I was able to cum in one session was 12 over about 45-minute session, but that was physically exhausting. Usually I would cum about three or four times in a session. A great feature is that it is like having sloppy seconds, or thirds, or fourths, etc.
Most of the later girlfriends were surprised at my multiple orgasms, but many of them liked them. Unfortunately, my ability to have multiple orgasms began to taper off as I approached 50 years old.
My one and only multiple orgasm experience was like the technique you described, but I have been unable to replicate it. Also, when getting near orgasm, my instincts are to thrust deeper and harder, not to slow down or stop!
To the original question, the most I've gone is 5 times in a little more than 24 hours, always with a wait time between sessions. With a past girlfriend, on a 4 day vacation, we fucked every day and twice on at least one day, all while being very busy with tourist type things all day long.
When I was younger, the most common was a night/day double header, or if I was really lucky, twice before sleep then again in the morning, or the other way around. As others have mentioned, in the earlier days of a relationship, the sex was more common, and more frequent.
I'm older now, and while I'd love to have sex every day, twice a week (sometimes 3), with my wife is nice and very enjoyable.