I personally cared for my father-in-law for 15 years until the age of 93; I had the privilege of watching him go from old to elderly to ancient.
He had Parkinson's and dementia, macular degeneration (legally blind) and deafness. Due to his war injuries he suffered daily pain, and I helped to manage his meds regime, working closely with his GP, and the NHS Pain Clinic.
This experience gave me a first hand understanding of supporting someone who was fierce in his unwillingness to lose his autonomy and independence.
I was able to help him weather each change and shift, learning to cope with each new level of degeneration of his ability to care for himself, each time moving him towards accepting a new level of advanced care that he could feel comfortable with.