As a person with serious mobility issues (I'm missing a leg, lol), I can say with authority that surviving very long on my own on a Doomstead would be impossible.  However, as part of a larger group of Doomers, it would not be hard at all, assuming the doomstead is properly set up.

I have 4 mobility devices, plus a prosthetic leg, crutches and canes. Two of my mobility devices are electric, a 24V electric wheelchair mostly for indoor use but it does function outdoors as long as the terrain is fairly flat and a 4 wheel 48V electric scooter for outdoor use.  Both use standard deep cycle 12V batts.  In addition if I have repair issues with my electrics. I have a standard manual wheelchair and I recently modified a knee scooter for use with my amputated leg.

I couldn't do anything requiring climbing or chopping wood etc, but I could easily run and maintain a hydroponic or aquaculture system, do food preservation and preparation and a variety of electrical wiring and plumbing tasks, although I'd likely need a helper with better hands.  A kid age 10 or more would do fine.

On the plus side, since I already live a pretty cicumscribed existence, I am already used to being stuck in one place so I'm over the cabin fever psychological hump.  I don't take any meds besides pain killers, which I could do without though it would be unpleasant.

My outdoor scooter has a 40 mile range on a charge, so as long as there are still some kind of stores open I could go shopping or trade goods with nearby doomsteads.  A small solar PV setup would easily keep my mobility devices charged up.

All that being said, it's pretty obvious that the medical issues you accumulate with age will shorten the length of the human lifespan back to where it was before the days of modern medicine fairly rapidly.  Going back as recently as the early 20th century, average lifespan for men was 65.  Go back to the 1800s, it was in the 50s.  The modern epidemic we have with diabetes will quickly kill off a lot of people once insulin becomes unavailable.  Even just bad vision will shorten average lifespan as prescription lenses become hard to find.  Many more women will once again die in childbirth and few premature infants will survive.

Now, there are these days quite a few Doomers well into their 70s still fortunate to have decent health and all their limbs who run their doomsteads mostly on their own or together with a wife of similar age.  Many of them do it as a refuge for children and grandchildren to come to when SHTF Day arrives.  It's a good retirement hobby for people like that.

I have no progeny, nor do I have any real desire to live any longer once we have reached the point in collapse where the power is sporadic, food is hard to come by and the society is coming apart at the seams.  I fully expect to be one of the first to go when SHTF Day arrives, and I am quite ready to cash in my ticket to the Great Beyond.  I consider myself along with Lou Gherig to be the Luckiest Man on the Face of the Earth, to have lived to see the end of Industrial Civilization and had a great ride to get here.

https://www.youtube.com/watch?v=nNLKPaThYkE

RE