Extended sessions, three, four hours, possibly more are indeed possible, and while maybe not common, there are ways for both men, and women to fuck for extended periods.
For those who don’t object to chemical enhancement, sex under the influence of certain drugs is one means to accomplish multi-hour pleasure sessions. Cocaine, Ecstacy/MDMA, pot, and probably others, perhaps combined with an ED drug like Cialis or Viagra are one route.
I commonly use the combination of good pot, and Cialis, along with a cock and ball strap to achieve a rock-hard, continuous erection, and delay ejaculation, to provide my wife pleasure for three to four hours at a stretch.
Many women, when aroused are multi-orgasmic, and have little, or no refractory period between orgasms. They can in some cases achieve nearly a continuous state of orgasm, with one or more hard cocks, fingers, tongues, and as long as they are sufficiently lubricated, either through natural means (cum, pussy juice) or artificially, they suffer no ill side-effects.
My wife has experienced several gang-bangs, in which she achieved a sort of fugue state of nearly continuous orgasm that went on for hours.
Very sexually experienced individuals and couples can achieve states of extended sexual orgasm; in males, this involves training and discipline to separate orgasm from ejaculation, and in women, the relaxation and desensitization training to transition from one orgasm to the next wave with little delay.
This extended orgasm, sometimes called extended sexual orgasm, or ESO is amazing. It is more difficult for men to become trained, because of the strong physiological connection between orgasm and ejaculation, but it is possible. The use of the aforementioned drugs can make this easier.
With the advent of ED drugs, used by men without ED, the effect is a stronger, harder, longer-lasting erection. Pot, moderate amounts of alcohol, Ecstasy/MDMA or cocaine act as desensitizers, and combine with some degree of self-awareness and self-control, the drugs work together well. The ED drugs will help maintain a firm, hard erection, generally as long as there is sufficient visual and tactile sexual stimulation, while the desensitizers help delay, or control ejaculation.
We’ve found, setting specific side-effects of drugs aside, that extended, multi-hour sex sessions are wonderful - exhausting, but other than soreness, usually joint or muscle pain the next day, from the physical demands and effort to maintain body position, there is little negative outcome.
For women, abrasion and minor tearing can be a problem, especially if insufficient lubrication is involved.
Otherwise, fuck-a-thon sessions are one of the most amazing things to experience, male, or female.