It's not in the male's genetic code to be monagamous anyway. Blame God.
However, the way I see it if you're thinking about it, you might as well hit it. Impure thoughts are the same as cheating in my book. If you haven't met your lifetime's personal quota of stellar fucks, you should still be single. The problem is many guys settle down long before this happens. Chances are your old lady will screw you over someday anyway and you'll be kicking yourself for passing up the high quality tuna you could've had. My guess is you're still in your 20's? Tap as much ass as possible now!!! Chicks start looking like shit after they've lived on dorm food and beer in college. Then after they squeeze out a kid that's their excuse to be 40 lbs overweight for the rest of their lives. The worst part is this look they get in their eyes around age 30 after being fucked and chucked 2-3 dozen times. It's almost like their spirit is broken and you'll be lucky to get a smile out of them in between them complaining about life and being tired 24/7.