I'm probably not a good example, I've usually been a "jack-of-all-trades" kind, but it's very often the very same way you did - you see jobs stop asking for a p

I'm probably not a good example, I've usually been a "jack-of-all-trades" kind, but it's very often the very same way you did - you see jobs stop asking for a particular tech and start asking for others (and it's probably too late to make a killing by then). No-one is asking me about my Novell NetWare experience these days :P . I do however work mostly with Microsoft products and they've given me a good run (from vb6 to .NET and my old SQL skills still serve me well). I do sometimes wish I'd picked up a fad faster (Ruby several years ago, React a few years ago, Blockchain last year and AI/ML this year).