I am sure comparisons between
myself 40 and my son 15
are different that between 70 and other age groups.
at the last, I don't feel the challenge of stamina is SUCH a big difference between us. In Fact, I think I have a good bit more patience... though my 15 year old son has made big strides in that.
...
another point to make, is that past 60 - once again between retirement and grown up kids, sometimes free time becomes much easier.
the issue at the age is surely health.
if your healthy, have a nice retirement fund; I could imagine the golden years to be a great time to be interested in chess.
+ some say it helps ward off alzheimer's
Never underestimate bladder control in long games.