Well, I was specifically referring to a single shoot. Retakes are often why you see some clips fade or cut to new positions, etc., instead of just seeing them scoot around to new angles. If you factor in retakes as well as how long they record on each individual take to get "enough content" for the final video they'll use, a day of shooting has to be a ton of physical exertion. They're constantly bouncing, thrusting, jiggling, rocking, or whatever else — all either while trying not to cum or with time to recharge and then going at it again for the next take — I can't imagine it's anything but a slog for them, a severe test of endurance.