In my youth I could easily masturbate to a full orgasm three times within an hour, but after that things dropped off considerably. I don't recall ever masturbating to more than six orgasms a day but that would be from the time I woke up in the morning to the time I fell asleep that night, so more like 16 hours than 24. After the third ejaculation the cum volume fell off noticeably but never went to zero in a "dry" orgasm.
I also have a very vivid recollection of a time in San Francisco when my wife and I screwed like the proverbial rabbits all weekend long. I had been on an extended work assignment and, in spite of jacking off daily, was horny as hell. She flew out and joined me for the weekend and it was straight to the hotel to get naked and fuck. Then a pleasant candlelight dinner and back to the room for another cum-filled session. After a couple drinks of wine and couple of hours catching up on each other's news, etc., we retired for the night, but not before pounding out a few more orgasms on her part and a third load on mine. It was early the following morning, about 3 or 4 AM, that half asleep I was only vaguely aware of having an aching rock hard boner and then came fully awake to realize that said boner was inside her again. That resulted in nearly an hour of slow, half asleep, easy thrusting and the fourth orgasm for me (thank God that she always lubed up well, naturally, to prevent any skin on skin chafing.) A few more hours of sleep and a leisurely breakfast had us back in the room for a fifth go around. Same thing after our late lunch, but those last two sessions took a lot of furious pounding and mental concentration on my part to finally reach the fifth and sixth orgasms. So in screwing I matched my six masturbatory orgasms within a day but it took a little over 20 hours instead of the routine 15 or 16 hours doing it by hand. Only managed to pump out half as many loads (3) the following day and then she hopped a plane back home with a smile on her face. Subsequent events led to the realization that the weekend in SF resulted in our much sought after first pregnancy, another reason the memory is so vivid.
I've always envied guys who seem able to do it again and again all day long with seemingly no end in sight. I have a friend in a distant town that I used to visit somewhat regularly who was like that. We'd get together for the principal purpose of his feeding me his cock and his load. He could easily shoot a couple of loads within an hour, and without ever losing his erection. I arrived one late afternoon for an overnight stay and he immediately whipped it out and sat down on the sofa. Within an hour I had sucked the usual two loads out of him and we cleaned up and hit the town for dinner, drinks and a little sight seeing. Later that night, back at his house, we shed our clothes and had a repeat session with him on the sofa and me on the floor for another two loads of cum out of a single erection. If it took more than an hour on this second go around it wasn't by much. After a couple of nightcaps and friendly conversation it was off to his spacious king sized bed and a good night's sleep. I awoke early the next morning lying on my back with him straddling my shoulders and face fucking me. That led to an extended sucking session, about an hour and a half, producing another two loads of cum. Although this time he actually went soft in between his two orgasms. Six loads in a little under 12 hours and hardly any noticeable decrease in his amazingly prodigious cum volume. The guy has to have the healthiest prostate on the planet. Just thinking and writing about it has me hard as a rock again. Think I'll have to come up (or is that CUM UP?) with an excuse to visit his city again sometime soon.