I find that subsequent orgasms do take a bit longer each time, to a point. But if I cum a certain number of times in a day then sometimes I experience the opposite and will end up cumming relatively quickly. This only happens when I masturbate though, for some reason with sex the time always seems to increase. Though, I get a lot more opportunities to go many times with masturbation. I suppose if I was able to have sex as frequently as I can masturbate then I might find the same results.
