I have a lot of sex as the outside man for couples. Wives are often very hungry, so extended sessions (over 4-5 hours) are fairly common. When I was younger, I could regularly cum 5-6 times (the last few with hardly any sperm). Now, I know how to delay cumming for many hours. This is in no way pounding the whole time. That is very much not my style. This is changing positions, changing pace, moving to oral and back to fucking, a break for a snack or something to drink, etc; but pretty much continuous sex. Also, my foreskin helps reduce soreness. So here goes the longest ones that I can remember, all of these without drugs:
Without sleep, in my twenties - cumming 9 times, lost count of her orgasms, noon Friday to around midnight Saturday/Sunday.
Without sleep, several times in the last few years - cumming once at the end or twice, around 8pm one day to around noon the next. These women were very orgasmic
With breaks for sleep - but fucking all day and much of the night in the room and on the beach, on an island with a couple I met there, 5 days.
One women and a group of guys, obviously with individual breaks - over 36 hours. (She was so blown out from repeated orgasms that she had to sleep for an entire day)
Orgy with over a dozen M/F - 3 full days