This is certainly not the kind of marriage you had ever thought you would have, but she long ago made it clear that this was the only kind of marriage that would work for her with you, and so you have no choice but to accept that this is how things are. A few times, you've come close to complaining about the fact that she leads an active social -- and sexual -- life with other men while you almost never go to social events and you're sex life consists of occasionally being permitted to play with yourself. But you knew that if you did say something, it would anger her, which is the last thing you want, and so you simply accept your lot in life as her cuckold.
The worse part would be the hours of silence wondering what they are doing!
I'm not reluctant, well not much, but I do find the concept of this exciting.