My wife has never fucked a "bull" but she has been with black men. Everything has pretty much stayed the same in our marriage except we now sleep in separate bedrooms, I'm not allowed to have sex with her, it's fairly normal for her to disappear for several days at a time so she can get her fix of BBC and this DAMN cage my cock is trapped in everyday.
J/K
It's sex and nothing more! It's a little escape from our normal life several times a year. We fuck like bunnies for several weeks afterward and we're better connected to handle everyday life. I think most people will find the best sex isn't when the other man is there with you but after he leaves.