I don't believe in sexually closed relationships. This springs in fact from my current 'religioius' belief system. I am an atheist and anti-theist. I don't believe in life after death, I don't believe in reincarnation, I don't believe you get another shot at this world so you BETTER enjoy it as much as you can NOW.
I really don't see what the sex hangup is. I mean if my wife wanted to go play tennis with one of her male friends they would both be excited have elevated heart rates and be sweating like mad so whats the difference between that and sex? Maybe sex is considered different cause you can catch preggers from it but G can't cause she's had a tubal so WTF does it matter?