Bathwater writes....
> Both my parents died within a year of becoming ill. I hope that is the way I go.

I hope that for myself as well. It's not something I have control over. I have seen people who have died quickly after their decline started. I've also seen the process take years. This is all complicated if the person isn't in constant pain. 

I'm not sure how death-with-dignity, assisted suicide, would work. My mother has had Alzheimers for years. I have an aunt who is basically a vegetable and has been so for months. They are not suffering. They don't, (can't!) realize they are burden to others.

For me to decide on a death-with-dignity, I'd have to be 75+ years old and still mentally fit, but seeing the first signs of dementia. I'm not sure I could make that choice.