75 isn't old, he's just hitting middle age.

Having said that, some of the people I meet in their 20s seem really old to me, and a lot of people in their 40s seem to think they are past it. You are only as old as you feel, so just make sure you keep on feeling. Bitcoin has become a product for the wise and mature, and not just for those seeking to experiment with novelty. You really need to understand modern economic and banking to take advantage of Bitcoin.