I'll be interested in y'alls perspective when you're 69 or so. The purpose of exercise changes to tone, stamina and flexibility. Also, I plan to exercise for the remainder of my life, to do so the primary focus is avoiding the only thing which will stop me from doing that, which is injury.
If you're unfamiliar, look at these guys... NEXT LEVEL AQUATIC TRAINING
If you're unfamiliar, look at these guys... NEXT LEVEL AQUATIC TRAINING