So basically, after the initial negotiations, you are "don't ask, don't tell." (dadt)

It's frankly, not optimal but it works. I've been doing it this way for 30 years, though sometimes it is difficult to convince others I'm not just creating an excuse. Sometimes the spouse just trusts you to not leave... but really doesn't want to know about it.

I'm actually the same way, no double standard. When I was younger, I just didn't want to know when she took lovers. Now, I would reconsider... but it's hard to change the rules after 30 years of success.

One reason 'DADT' can be difficult, is part of my personal promise was no one we knew in common. Eventually you'll meet someone mutually and you will feel the chemistry... maybe overwhelmingly so. Did you discuss "limits" in that context? Another is that you come to have feelings for a play partner and it makes you feel good and you really want to share that with your spouse (or maybe you only do if you're poly)... but you can't.

So before you "close" the negotiations, if you haven't done so already, you might want to raise those concerns/questions.