Wife likes them young

I came home early from work one day and caught my 35 year old wife with the 20 year old next door neighbor. I just walked in and all I could see was his ass pumping on top of my wife. I just went into the kitchen and grabbed a beer until they where done. They came out later and he ran out the door, she just poured a glass of wine and sat down.
I could not blame her, his body was young and perfect and I have a hard time getting it up. I was 50 at the time. They had been screwing for almost two years since he just turned 18 and she continued to see him for another year until he moved away. Then came another and then another and on and on. She is just the kind that can't go without sex and she likes them young and since she is really hot she has no problem finding men.
We are everything else to each other except sexual partners. I guess if I was any kind of man I would not put up with it but here we are.