For those who claim to have advance planning (trusts, executors, POAs, etc) all setup to take over "when its time", be aware that all of that can be thrown in the trash can if you get dementia.
Dad had designated me as POA, co-trustee, joint on his bank accounts, and turned over administration of his finances (rental properties, insurance, etc) to me to admin.
Problem is he forgot he did any of that. And the kicker is, at least in Arizona, the court lets a diagnosed dementia patient chose who their conservator is going to be.
Since Dad was mad that we (his lawyer, his CPA, his insurance agent, his property manager, and his family) disagreed with Dad's plan to give his home health aid a house and move in with her instead an assisted living facility (for which he has an LTC policy), the court let him fire all of those entities and throw out 15 years of estate planning. The court agreed he was incapable of making his own decisions, yet let him chose a 3rd party conservator (who is totally incompetent and whose only contribution has been to bring another lawyer's (hers) mouth to the feeding trough).
You may state (now) that you trust so and so, but when your bag of mental marbles is half empty to the point you've lost your ability to reason or control emotions, you might not even remember who that person is any more.
I have not found a dementia proof advance directive document to facilitate a transfer of authority "when its time". All of it can be rescinded by the patient short of maybe an irrevocable trust. If anybody has solved this problem, I'm all ears.