Age is certainly a factor. Herbals can shut down erections and cumming. Google Chasteberry.
I've been a Cuck for over 20 years, before I even knew what the word meant. I haven't had any intercourse with my hot-wife since 2011. Over the years, I've forgotten what pussy feels like and my cock never gets hard enough to fuck anyways.
For the past 3 years, she's gone totally Black, and gets laid about twice a month. Over this period, no wonder she has lost interest in any kind of sexual activity with me, and recently stopped all contact with my cock. I've let her know I'm OK with this and let her know I enjoy her activity with BBCs. The only time I get any pussy from her is after she has sex, I get to lick her pussy after her guy leaves when she's not too tired.
We both enjoy each other and our marriage, but prefer this lifestyle with her sexual activity and satisfaction being at the center of our sexual relationship.