Now they are in their 60s and same work they did all their life (leading economical department of 3 high schools with various rental properties, manager at metal engineering company having at one time 300 subordinates), they would barely manage. Memory starts to go down too.
At this rate, it will last them well into 90s to be OK for anything ordinary life can bring, but to ignore this is to ignore reality right in front of me.
Maybe there is some other factor, like constant hard training of the brain by having ever-evolving creative work instead of kind of same office work, or some other aspect.