I Have A New Wife

I have been married 19 years. Haven't divorced or found another wife. But a year ago my wife changed (drastically). I wasn't happy, but I either had to learn to live with it, or lose her.
It started a few weeks after her 40th birthday. One evening our son did a dine and dash, headed out to a friends house. As we sat at the dinner table she calmly said "we need to talk". Again, very calmly, she informed me she was fucking a younger guy she works with. I didn't say "affair" because she made a point it was just sex. I was caught off guard. She flat out told me her sexual needs have increased and she intended on meeting them, even it required more men. She gave me the gloss over, of telling me she loved me, no intention of leaving, all that crap.
Strange as it sounds, I let it happen. It got to the point I began asking questions about the other men. Wasn't happy when I found out she had sex with a couple of my friends. At that point we kinda came to an agreement. I somewhat (when I wanted to) became involved. She promised no more friends or anyone we know unless I approve. I have been present and watched a few of her meetings with guys. Even joined in once. I am pretty used to it now. Having this new wife isn't too bad.