You've got to be kidding me, right?
It's okay for a man to sleep around in a relationship, but not a woman? What are you smoking?
Marriage is all about trust. Either you both openly sleep around and talk about it with each other, or neither of you do. Anything else will lead to misery.
What I'm saying is that every 'older' guy I talk to about marriage, they have ALL told me about their wife losing interest in sex around middle age (which can be as early as forty something) as well as not getting much when the children are small.
So would you rather be a frustated angry man, who ends up divorced or sleep with some random girl once in a while?
And there is a major difference between men and women cheating even if you choose not to believe it. A man can have an affair and love his wife just as much. If a woman has an affair it generally means she doesn't love her husband anymore. Also, marriages based purely on passion lose out to marriages based on respect and common values. But then the sexual attraction can be less sometimes.
Of course, I generally just think it's a better idea to stay single and have sexual freedom, unless you want a family with a woman you love. Never understood why young guys get in one long relationship after another, then break up after 1-2 years, then suddenly are 30 and have never had any real freedom. Serial monogamy is a weird new thing.
All in all, I'd rather be honest, at least to myself, that I'm going to have a hard time being monogamous for decades, than being all holy and then ending up divorced because I was tempted years from now.
So many people cheat and lie to theirself about afterwards ('he isn't giving me enough attenton', 'she doesn't want sex with me anymore') and that's why divorces happen.
Plenty of countries accept that affairs are normal, particularly for men. The french President Mitterand had a publicly known mistress for years while being married to his wife.