Still being a bit more than 20 years away from usual retirement age, I can't speak for that aspect of this.

However, one of the biggest killers of retirees is loss of purpose and drive. So, having a way to help others deal with problems your greater experience gives you insight into, is a great thing, not just for those who benefit from your advice, but also for the retiree directly.

Thus, great idea.

Interestingly, I ran into someone with a problem they absolutely couldn't solve, that was easy for me to solve, because they'd never edited a .bat file before, didn't even know what they were. I grew up on DOS, so it was simplicity itself for me to show them what to do and how.

Experience with legacy systems can also translate directly to "experience with the hidden parts that they don't teach you any more of current systems".