My lady partner and I have practised lovemaking probably about 5 or 6 times in an hour and a half, two hour peroid. However, I need a break after I finish each time, but if I keep myself busy with her then I can soon rise to the occasion again. After a while it'll start to hurt me, and start to hurt her too. I guess you can get too much of a good thing.
The penis naturally loses blood after ejaculation so will start to become flaccid again.