Your wife expects to have desire for you in bed. A long time spent in preparation is probably indicative of her attempt to 'get ready'.
She mentions therapy. She is trying to figure out how to desire you by desiring sex. She is obviously trying to reason out her lack of physical response.
At 51, intimacy is the real issue. Intimacy is a salve and a balm for wayward hormones and interruptions in physical desire. It is the thing that allows for her not to be horny and still enjoy time spent in sexual encounters with you.
Instead of threatening to walk, try and work with her on a plan to create intimacy.
Whether or not she makes efforts at a level that you approve of, she is still making an effort. That is something that you can work with.
She obviously wants to make it better for you, and HER. It is not unreasonable that she should be able to get something out of having sex with you.
If at all possible, work WITH your wife on this issue. Demanding that she become an opera star when she can barely sustain a note will not get you far. It takes lots of practice first.
All the best, -NOPkins-
I will ferret out an affair at any opportunity.
-An affair is the embodiment of entitlement, fueled by resentment and lack of respect. -An infidel will remain unreachable so long as their sense of entitlement exceeds their ability to reason.
