My boss at the NIH was in his late 80s when I started working there, early 90s when I left. There was an obvious physical decline into complete frailty during those four years, but he was as sharp, lucid and stubborn as ever. You don’t get to work into your 90s unless you have it your way, and “the way” became shorter hours in the office with prolonged nap time, sometimes during meetings, while maintaining the final word on anything that happens in the lab.
So, “the mind is willing but the flesh is weak” often came to mind, and until we develop a Futurama-style brain-in-a-box there are limits that biology imposes which can’t be overcome through force of will. You hate to see it, but we will be seeing it more and more often as the Baby Boom generation gets into its sunset years. Not because they’re any more selfish than other generations, mind you (my old boss was of the Silent generation), but rather because they are the most numerous and the biggest beneficiaries of death-delaying medical advancements.
It seems to me that the higher up the person is in the hierarchy and the longer they have worked in the field (my boss spent 60 years at the NIH), the harder it is to imagine anything other than staying on the job until an act of God intervenes. This is exactly what happened; I was gone before then, but there were many in the lab who were left scrambling for a new position, taken by complete surprise that their 90-plus-year-old chief was no longer with us.
So it goes…