My wife told me beforehand that it was very likely she'd want more once she had the first good sex with another guy, - a coworker. She warned me that I'd better be sure this is what I wanted, as there'd be no turning back. And there wasn't. But given the constraints of work, family, and all the other stuff in our lives at that time, it was a twice a month thing. Sometimes more if she spent the weekend with him. The "logistics" of it all can be challenging. Then add in her monthly period.