My Mom passed at 83. She smoked for 60 years, and managed to realize her greatest fear - she trailed an O2 tank for the last year or so. She had increasing dementia but was very frail physically, and all four of her kids hoped that her body would give out before her mind did. We felt it would be much kinder to her, as she was a wonderful, caring person and you just don't want your mom to be helpless. As it turned out, her much-abused lungs and frail body gave out first. Her memory had dwindled to about a 5-minute window or less, but she was still there and still mom.
My family and daughters visited her the winter before she passed (she was 1200 miles away in central Washington, in a very nice senior care home near my brother's family.) She was very concerned about giving our girls (ages 14 and 15) good advice about how to conduct themselves, and did so about four times while we were there - the same advice every time. It really drove the point home that she cared about what she was saying.