Logic tells me that it’s probably just part of the process of getting older. Less energy and less inclination to keep holding up the mask, a little less caring of what others think, grumpy old man syndrome, etc.
These examples seem to be related to normal aging process that everyone goes thru. And I have read people express the same ideas quite a few times on autism forums. Personally, while I do believe it can have an effect on our autistic side, indirestly, I would guess it would not change the nature of our autism itself. Like I wouldn't expect autists with poor face recognition to suddenly see an improvement after age 50, etc. I could be wrong. I really haven't seen any studies that look at this aspect.
For me the physical and to some degree mental deterioration is obvious and automatic in a sense. I don't have to work at things wearing down. While my autistic condition and awareness follows its own path based on level of understanding, what I have learned. So while some things are harder, I am better equipped mentally to handle things better. That too will go down the tubes eventually I suppose, if I last long enough to engage with senility.
But at this point I try and choose the optimistic outlook. Autists do apparently have shorter lifespans on average then NTs. Multiple studies are validating it. One recent study (article with link below) has my average lifespan at 58 years. So I have already beat that by 6 years and counting. So while things may be harder, technically I shouldn't be here, so I see that as a winning season.
Why Do People With Autism Have a Lower Average Lifespan?