Pre-nup negotiations work two ways - make them too unattractive, and the trophy wife moves on. Gotta be something in it for her. Other than the prospect of nursing a declining 80+ year old through his last few years. Sometimes I get the impression that trophy wives might not have examined the long term quite carefully enough.
A close friend of ours is dealing with the age difference thing, not because of the trophy wife game but simply because she and her ~15 years older husband got together years ago when 15 years difference didn't seem like much of an issue. Well, he is now almost 90, and you better believe that the difference is a big deal now. And he is still healthy. The difference in physical ability and interests is now huge, and a serious limitation and frustration every day of her life. I would not wish it on any woman, or man for that matter, although men find themselves in that trap less often, and usually because of health surprises rather than original age differences.
Happy growing peeps, garden or otherwise.