We just hired a guy out of retirement a few years ago. Retired after 30 years of C dev but wanted to keep busy in the small town we're based in. He's beloved by all of the software devs and the cyber team (we're basically two companies in one). The first week he was asking questions about how git worked. Then like a week later he was explaining why massive amounts of python code we wrote for running simulations was inefficient and how it could be fixed.