Condolences nimblehunter, losing a best friend is really tough. You know what they say about friends and family, you can't pick your family but you can pick your friends. And "best friend" is quite a statement. Good on you for giving your best friend a proper send-off.
that's what is called "doing the right thing"
I hesitate to bring this up on this thread and this is in no way a comment on nimblehunter's best friend because I know nothing of the circumstances. But I've thought the same thing Mannlicher said above. Alzheimer's seems to run in the family and there's no way I want to be a burden, or spend my kid's inheritance for a spot in a warehouse for dementia patients. So I've thought about ending it if I get the diagnosis, before it's too late and I lose the capacity to act.
But just recently a good friend at work had his father-in-law take his life. He had multiple medical issues including memory loss, but it was totally unexpected and the family was devastated. He chose to end it with a bullet so that no doubt had something to do with it the family's devastation. My friend told me to consider that if I ever got to that point. It sounds like nimblehunter's friend's situation was totally different and friends and family were prepared, what with the send-off. Just something for the rest of us to think about.