A lot of older programmers I've known fell into the trap of maintaining one component, working with one technology. They probably felt secure that it would be too difficult to replace them, especially if their code was unintelligible. But this, invariably, did not work out. And then they are left without current and marketable skills. I don't know if the passion for acquiring new skills weakens later as I'm still in my 30s but if you no linger have a built in drive, you must cultivate one to stay relevant. But, some programming skills remain relevant regardless of language or platform.
please, please read "Design Patterns" by the gang of four and "Clean Code" by uncle bob. They should be required reading in every CS curriculum. Sadly they are not. Those books? Recommended to me by an awesome white haired software architect.