It's very difficult, isn't it? I had some friends in their nineties who, until about six months before the husband died, were both active independent people, still able to manage and maintain their house and a large garden. They had some help with cleaning and gardening, but were making all the decisions and enjoying a very full life with lots of gallivanting. My friend, the husband, deteriorated very quickly in the last six months of his life, although still at home and supported there.
His widow, though, now 92, is completely overwhelmed with trying to manage this large Grade II listed house and its garden and lost without her companion of over sixty years. I would have said to most people to understand earlier that you're moving into a different stage of life and will require different things and make decisions then about where you live etc, but they clearly managed and thrived right up until nearly the end of their lives.
Sounds like they've been lucky, last six months excluded! It's something we all need to plan more for. Grim!