I do this and I love it. Honest to God, my favorite thing in the world is to watch another man fuck the hell out of my wife, unload inside her, and then dive in as soon as he pulls out and devour that wonderful creampie. The first time I ever did it I felt ashamed knowing that this guy had just fully used and enjoyed my wife right in front of me in our own bed, and was laying there watching the husband of the lady he just scored with eat up his extramarital cum. But I was more horny than ashamed, and I'm so glad I took the plunge! I've gotten to lick her and the cock fucking her at the same time, but haven't yet found a guy who's cool with letting me suck him clean after he's orgasmed.