A long life?

A long time ago, my dad told me that he would never want to live to be 90 years old. I think this was when my grandmother was 90 and was struggling with dementia. She was in a nursing home and was always confused and sad. Her quality of life had diminished greatly.

While I could understand why he said it, I always dismissed his statement, telling him that it would be great to live that long. Think about all the changes you get to see! Sometimes, you get to meet your great-grandchildren! You get to enjoy retirement! Go on lots of trips! Part of my excitement was that when you're 22, you can't imagine in any non-abstract way that someday your life is going to stop. There's just too much ahead and too much to look forward to.

I have revisited this issue many times. Dad's statement turned out to be prophetic, when he died at age 61.  It was with grief that I thought about how Dad would never live to be 90, never get to meet his grandchild(ren?) (let alone great-grandchildren), never get to enjoy retirement. Then, our neighbor died recently at age 95. She did actually get to meet her great-grandchildren. But she also lived through the death of her husband, all of her friends and, truly, her generation. She was blind and going deaf. In some ways, she was still happy - she retained her quick wit and her sense of humor. She lived in her own home, near her daughter, and saw her nearly everyday. But I think she was still sad and lonely. 

So I return to the question. I suppose it's somewhat insignificant to wonder about it, since in the end, you really can't choose how long you live. But is it better to be the last to go, and follow the lives of the younger generations? Is it good to be the one who tells the stories about all the people and places that are long gone? Is it possible to be happy, if that ends up being your lot?