[Catch 22]

I'm late to the party on this topic, but I'd much rather bust early than think about non-sexual shit. There are some other good ideas already(the 50 year old guy nailed one of them), but you can also work in positions and angles that you aren't as in to. So go to your favorite, then one you're into quite as much for a "rest," then back to something you like a lot. Same with speeds - going too slow or too fast moves me away from climax...you can use that to your advantage if you have to. But c'mon, Margaret Thatcher?!?!