Hello Hash...I hear you. My wife was also not interested in sex so much, which was very frustrating to me. Being a Christian, I could/would not try to find it elsewhere. I felt it was very unfair and reading posts on the forum where men and woman really enjoy sex, brought me great despair. After the divorce, I could obviously find another woman (and there were a few), but it is just like you said, they loose interest as they get older.
It is because of THAT AND the constant sexual clouding of the mind, that I decided to get rid of my genitals and sexuality. Now, for an 'every day' kind of guy, he would never even consider it, but as I disliked the looks of a penis and testicles from a very early age, the decision to remove it was not difficult at all. That is maybe why I do not regret this action or feel intense frustration. There were moments when I missed my penis, but it is just for a minute or two when I look at a girl and 'knew' I could make love to her if I still had a penis. But, looking in a mirror, I am reminded of my age and 18 year old girls don't take guys of our age...normally. I really like girls between 18 and 25. Those are their best years...sexually...imo.
Anyway, your wife had a hysterectomy, and she is not less of a woman. If she should get breast cancer and they remove it, she will still be a woman and loved by you. Our bodies are just 'tents' in which we live. People loose their teeth, eyes, limbs, breasts, genitals, hair and minds

Go for it, she will always love you.
Regards old friend
Penectomy feels amazing and I know you will love it...IF that's what you want.