I don't either..Okay that's a total lie...To be honest its all about fantasy and of course you're not doing it to the point where they fall unconsciousness.
I love having my ass licked and just having my crouch smothered with his mouth. If I control his breathing a little bit, so be it but I more or less get off with the fact that I'm using him as a chair and he loves it so much he has to lick me to keep me there.
I would definitely be down for that.