Sifu Roy holding The Bagua Zhang Guard Posture
One can increase the probability (hedge your bets) of being able to move and think clearly longer as you age. Are you curious?
This increase in longevity that I'm thinking of, is the effect of regular practice of internal cultivation practices like T'ai Chi Ch'uan, Bagua Zhang and Qigong/Neigong.
One of my initial attractions to internal martial arts was watching older practitioners that were still able to practice and move like a much younger person. I've personally witnessed a 90+ year old, look like a 40 year old, from the back as he was walking away from me.
There are no guarantees but if you can learn and practice arts like T'ai Chi Ch'uan, Bagua Zhang and Qigong it is highly likely that you will be able to move and think clearer as you enter old age. These arts are specifically designed to be practiced well into old age.