This isn't something I've put a lot of thought into. I think maybe because my dad lived to be 78 and was mentally sharp right up until his fina few days of drug-induced unconsciousness. Both of his parents and both of my maternal grandparents lived into their 70s, and they also never displayed any signs of dementia.
I know dementia isn't strictly genetic, although there appears to be at least some genetic component to Alzheimer's disease. I really should think about a plan, just in case.
Thanks for the thoughtful story!