Always wanted to do that... I've long had a fantasy of watching my wife get the snot fucked out of her by another dude, maybe several... filling her cunt with cum, then I get to go afterwards.
Sadly, when we first tried swinging and I was almost going to get my fantasy, the dumb broad fell in love with the other guy and ran off with him. She was only supposed to fuck him, not break up the family. Let that be a warning. Be careful what you wish for...