While I'm a mere 40 years of age, I have gone through the downsizing process already. Basically, I stopped the trend I started years ago, going from 35mm to 120, and then 'graduated' to 4x5 via two different cameras, and finally 5x7. Upon acquiring the 5x7 I stopped and wondered why I was doing it, and sold off my 4x5 kit to focus on medium format.
My realization was that I really didn't see any benefit to shooting 4x5 compared to 120. Quality of the final print is not even a consideration, because with good medium format lenses, and films like TMax, Acros and Delta, it's already ridiculously good. It's maybe besides the fact, but since I've fallen in love with the 35mm format again, and prefer it over any other camera.
So for me the downsizing was primarily for practical reasons, but it also helped consolidate my camera collection, growing with all sorts of unnecessary gadgets that I really didn't need, and just boiled it down to a few really solid cameras. Hasselblad 500 system, Leica M2 system, a Pentax KX system, and a nice Rollei 35. Those are my main cameras and I really don't see much need to ever get something else. Finally, it does offer some health benefits for me, simply because I am very tall, and sense budding back problems that will only get worse by schlepping around an enormous backpack.
What it ultimately resulted in is the use of fewer cameras, which means more consistent output. It helps me get more familiar with each camera I use, to the point that they are very much second nature, and intuitive tools to use. The benefit is that they get out of the way when I use them; I don't have to think about what to do. This also helps me generating more consistent output.
So now there's this profound peace of mind of knowing that whichever camera of mine I pick up and use, it'll be an intuitive tool to just enjoy what's in front of the lens, creating negatives that I know practically at the time of exposure how they need to be printed in the darkroom. I recognize negative contrast upfront, focus and depth of field, and also have confidence that I nailed the shot, for the most part. There's tremendous freedom of creativity in that, because now I am free to focus on the areas where I most need to improve - with vision, content, gesture, emotion, framing, and so on. I'm a staunch believer that simplicity helps vision; getting away from focusing too much on the camera, equipment, film, developers, etc, is a step closer to getting down to what truly matters - the prints.
My point is, regarding your request, that I don't think that necessarily age has all that much to do with it, but rather to find something that suits our vision, our idea of fun, weed out the unwanted elements that get in the way, and select a couple of tools that help us achieve what we want to achieve. The benefit is that this allows us to really focus on the photography, which to me IS the print. Without it, there isn't photography.
I hope that makes sense, and that it might contribute some inkling of benefit to the choices that lie ahead for you.