OP, over the years, I've come (no pun intended) to believe that this is a very common situation. We get older and our wives lose interest. In my case, the sex grew less and less frequent. Adding to the decline was me being so tired all the time, and my wife having a bum knee so there was virtually no variety in our positions. I would love, LOVE, to do her doggy style or, even better, have her ride me cowgirl or reverse cowgirl. But... nope, not with that knee. And there's no more oral or "digital" sex, either. We still love each other but... you guys get it.
In addition to the slow (and perhaps arguably
natural) decline in our activity, I found that since I'd dropped my last gym membership, I was actually missing being in the locker rooms, showers, saunas, and steam rooms with other naked males. I gather now that nudity is a bit of a no-no (which is absolutely absurd) but back when I did go to gyms, it was unquestionably the norm that guys were naked, walked around naked, showered naked, and so on. So it was that I found myself, an older guy, missing that... that... well, whatever it was about being in the company of other naked males (whatever their age). I also found myself thinking back to the few boy/boy situations I'd had all those decades ago but now with a completely different attitude. And as I've spent more time online discussing such things, and reading other guys' experiences (not just gay guys, but guys who considered themselves straight), it appeared that most boys had multiple incidents with other boys. I didn't, really, but I started to "what if" my memories (what if I'd done this, or what if I let him see that...). The bottom line is that I wish I HAD shared my naked, fit body with the boys who wanted it. I wish I hadn't reacted with horror the two times I realized I was becoming erect because of seeing another boy naked. The first such incident, I was about 15 and the other boy was my pre-pubescent little cousin, about 10 1/2 or 11. The second incident, the naked boy was my best friend in high school, a boy I'd seen naked many times every week for almost three years with no such reaction (we were 17 or 18 when it happened).
End result - these days I LOVE seeing photos of naked males just as much as I've always loved seeing photos of naked females.
Sigh... hindsight is, indeed, 20/20 and youth is, most definitely, wasted on the young!