Since I am an older divorced woman, I will tread lightly here. I think it would be beneficial to discuss what DOES work in a marriage, rather than what doesn't work.
The first word that comes to mind on this topic is the word "intimacy". Maybe it's somewhere on this thread, and I just missed it. To be "intimate" with someone means that you have to let your guard down and be vulnerable. It means the husband and wife have to talk about their day, their thoughts, their emotions....all the things that frat boys and misogynists hate.
Our bodies change as we get older, but if the "husband loves his wife as Christ loves the church", he will protect and love her even through old age and saggy skin. Of course, we live in an age where a man can find all sorts of things on the internet, and it's easier to click on the young attractive women who don't share the family bills and other issues that must be discussed in a marriage.
Lest any of you worry or think your wife will lose interest when she turns 50, think again. It's not necessarily so. The main thing is to listen to each other. Your spouse might have insight that never occurred to you, and it could have something to do with a physical problem that a doctor could address.
Trust me, it's much better to intentionally listen and respect your spouse, than go through a divorce, which brings out the worst in people. It dissolves a union between two people who promised to cherish each other until death separates them.
I've heard it said that the biggest sex organ is the brain, and I believe it. As you grow older, hopefully your marriages will grow richer. I pray that for all of you.