If it happens, extremely exciting. Any tips for stamina in the face of overwhelming stimulation?

Ian Kerner: I've heard from guys who had spent months trying to set up a threesome -- convincing their girlfriend and finding another woman -- and then when it finally happened they orgasmed 40 seconds in.

Then the girls went on to have a big night without them.

Just as when you're having sex with only one other person, you have to be aware of your own body. Know your point of orgasm inevitability, and when you feel like you're getting close, which is likely to happen much sooner in a threesome, pull back. This can mean stopping all genital stimulation for a bit or just slowing down.

If a guy is really worried he's going to orgasm, he can practice a popular technique for "PE," the squeeze technique, which works great for dialing back arousal.