I'm afraid that once I'm at an "orgasm" there is no turning back... In fact, I actually think that your brain turns off and just goes into squirt mode. Seriously.
Um as far as a boner turn off... yeah that is possible. But I've never been able to go from hard to soft very quickly, not by thoughts at least. Its like once the blood is in, it aint going anywhere for a while. Guess my viagra % in my blood is higher than others... lol.
The only thing that can make my boner go down quickly is a crazy change of events, like someone busting in the room while I am wanking it or something. lol