[mkozlows]

100%. I think this is the biggest trap that an experienced developer can fall into. "I know Tech X, I can still get lucrative jobs in Tech X, there's no reason for me to jump out of my comfort zone and learn Tech Y."

But if you don't do it, you're stuck on the local maximum of Hill X, and as it gradually erodes away, one day you realize that you don't have any lucrative jobs that you're qualified for, and you're so far away from what Tech Z is nowadays that you're effectively starting over from scratch, except that also you need to unlearn a bunch of stuff that's no longer true.

And this happens fast. If you try to coast for even, say, five years, so many of your skills will have turned to dust.

This is why the only real way to have a long-term career as a developer is to genuinely be interested in this stuff for its own sake. You need to want to go learn the latest new tech not just out of a cynical career calculus, but because you think it's genuinely cool and interesting and sounds fun. As long as that's true, I think you'll be able to be a valuable dev even as you get older; as soon as it stops being true, well, time to consider what's next for you.