At age 67, I agree with this. I am not in the best physical condition in the world, but I do exercise a lot. This enables me to keep up with the youngsters with whom I do tech diving, and it enables me to teach tech diving to those youngsters. In that world, I do all my share of the physical activities, like carrying gear and setting up facilities. No one does any of my work in consideration of my age. My gear includes Worthington LP 108 doubles, which weigh over 100 pounds with the manifold and tank bands. Add a backplate, regulators, canister light, backup lights, etc., and you are starting to talk about real weight.
Most of the diving I do these days is technical. I will still do two deco dives a day in the 200 foot range, but if we are going much deeper, I will only do one. I will do a 250+ foot dive in the morning and then shallow, training dives in the afternoon. I am planning to do a trip to the south Pacific next spring, so I will get in a good load of regular, recreational diving. I will do those dives with two friends my age. We dived together in Bali last year, doing three dives a day while we were there. Before that we were on a liveaboard in Australia, doing 4 dives a day.