[ghaff]

The flip side is that, if expertise in XYZ is no longer valued, that can be an issue. I've known people who were essentially the world experts in some narrow area of technology or business and that became irrelevant which was a tough situation to be in.

It's easy to say that people should keep skills up-to-date but if you're truly a world-class expert in X, it's hard to transfer that level of skill to Y. That's a different level from junior competency in one language picking up another language.

I know someone at a largely military sub talking about bringing in "geezers" to consult on some very specific classes of problems.

[unnouinceput]

You misunderstood me. In my example XYZ was a combination of specific Windows API's to be called, not a technology. For the foreseeable future Windows is here to stay, and regardless of the programming language used if you learn its API's you'll be king.