For many years, I have been perfectly content with watching my wife fuck her bf, cleaning her pussy and sucking his dick clean. Denial is a big part of my turn-on, so when my wife has a regular bf, or a live-in bf, I like being denied vaginal sex with my wife and letting her bf be her primary, if not sole sex partner.
Me being bi-sexual is a big factor, as well. I love sucking cock and my wife loves it when I suck her bf's cock and swallow his cum. In fact, she encourages me to suck his dick a lot, lol.
My wife and I are in our 50's. Her current bf is a well hung, 30 yr old stud, named Kirk, and he practically lives with us. I gave him ownership of my wife's pussy well over a year ago. So, for well over a year, my wife has only had vaginal sex with Kirk. Kirk has a beautiful, muscular body and thick, 10" cock. He is truly gifted and my wife and I are very lucky to have him in our lives.
My wife does still suck my dick at times, while Kirk is fucking her. My dick is small enough for her to fit the whole thing in her mouth and she kind of likes that.
I love knowing my wife's pussy has only felt Kirk's dick, instead of mine, for well over a year and I love knowing that my wife carries Kirk's sperm inside of her, practically every day, instead of mine.
I am perfectly content doing clean-up duty on my wife and sucking Kirk's dick. That is the definition of sex for me and I love it.