Learning new things is how you keep your mind working. People who sit around doing nothing in retirement tend do die sooner than those who keep busy. What you keep busy with doesn't matter, just do something challenging.
Strong agree. There is enough to learn in one's professional career that keeping up to date on tangential technologies may not be worth it until you have a need.
Having hobbies where learning and applying things is not just fun but can also scratch that itch to keep your mind fresh.
Agreed. I feel the need to learn new things just to keep my learning muscle strong. Sometimes I actually need to learn a new thing, and if I haven't done it in a while, it's scarier.