It's one thing to be older. It's another thing to be rational and of sound mind as an older person. At some point, it's time for grandpa to retire.
My dad's at retirement age yet continues to work on bleeding edge harness engineering and cloud security work, yet there are plenty of 30 and 40-somethings on HN that don't know the difference between a CNI and kube-proxy let alone are bordering on unemployable due to personality and educational skill deficiencies.
And my granddad's still physically active as a farmer in the old country. And his parents were alive and active into their 90s (also as farmers).