I have a girl that is attempting to make me loyal right now. As a tactic to get this good sex, I am playing along, but it's been about a month and I'm starting to want more variety again. There's been a few brief periods of monogamy in the past decade or so, but it's not usual for me at all. For me, it's all a game. I never get too close to women, so it works out fine for me in the end.
Women will attempt to play the shit out of you. They are MASTERS at this. Women are masters at psychological manipulation...they learn it from a very young age. Women are also masters at reading social cues. This makes them at a much higher level than men psychologically. Guys are the dumb ones. Don't be the dumb guy. Be the 1 percent that understands the game.
It's better to have multiple women that you are fucking/dating. This serves 2 purposes: first, it makes women want you even more. Women ALWAYS want the guy that other women want. They love the challenge of fighting for your attention. Second, it assures that you never get too close, and this will end up saving your mind, soul, and bank account in the long run.