I guess Latinoman and cordoncordon have a point there. Cheating on his girlfriend like testiculz did is nothing but immaturity/insecurity hence the need to shove his penis into a warm body as some sort of validation or ego boost.
That's actually kinda sad.
The way I think of committed relationships is the following: assuming you're a great looking. witty confident guy who's got no trouble whatsoever getting laid then I guess it is also safe to assume you wouldn't be on a LTR unless the girl is special enough to be with her and be with her only. Now, if she's that special, why run the chance of messing it all up for a quick shag? And if ruining the relationship doesn't mean sh*t to you, then that means the girl isn't that special and you should've realized that before and dump her then.
Now, I think one of the greatest things about LTR is they allow you to use all the time and energy that you would spend getting pissed with your friends and chasing girls in bars and clubs for something far more rewarding, wether that means learning a new language, changing jobs, learning new skills, hitting the gym more often or simply spend some quality time with someone you want to be the mother of your children at some point.
I guess what I trying to say here is: a boy will spin plates by getting laid with a dozen girl a month and that's alright, but a mature man into a committed LTR will spin plates by keeping himself busy and succesful at work, developping new skills and interests to ensure a healthy and balanced life where everything does not revolve around his wife/GF.