That is a good point. In terms of my great grandmother, she was on death's door before my grandmother and mom flew to visit her for a week. While they were there she was doing alright, but as soon as they left, she went back downhill pretty quickly. I'm just glad that her type of dementia isn't genetic (most types aren't anyways according to the latest research). She was just lucky, or unlucky depending on how you see it, to live this long. Something similar happened to my great grandfather on the other side of my family. He lived to be 99 and only got 'off' the last month or so of his life. He never lived long enough to be formally diagnosed with dementia.