I'm in the same boat, pretty much. Sounds like you've got a bit of an age lead on me. But I've been monogamous since I got hitched back in the early 90's. It's good stuff, monogamy. I like it.

There was a point about three years in when things got dicey. Left my would-be fling at the bar, unflung, as it were. Went home. Said to my wife, "Look, I almost did something stupid out of sheer frustration. We need to fix this." We did.

For me, monogamy just kicks so much ass.