As a young person, I am shocked and horrified by the idea of being 70.
Yet I suspect that when I am 70, I will want to live one more day.
Personally, I will relish the day when I can pass off being a curmudgeon and telling people to sit-and-spin as dementia.
And if, by the grace of medical advance, I cannot, I don't see why I'd have much problem with the loss of my excuse.
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: