I have thought a bit how to respond to this comment. From the folks I've "grown up" with, the ones who got stuck either specialized in something that became less relevant, or failed to branch out beyond things that can be learned in a few months. I think it might be useful to unpack both sides of that.

Specialization is fairly easy, people who were getting "top dollar" as large systems enterprise architects (big SMP machines like Sun and SGI used to make) had a skill that is not useful to the newer enterprises that are outsourcing their infrastructure to SaaS/PaaS/IaaS type companies. That continued to be great until it wasn't, and then it really wasn't. When someone looks at their resume they see someone they have to retrain to the new way of doing things.

The second are folks who were always building things with technologies that were fairly recent, but at the end of the day they could train someone to produce as much code as they could in a few months. That is a good skill to have but you have to realize that your experience is perhaps worth a 2x or maybe 3x multiple on a starting salary, period. And once it gets there, that is where you are. The rapid influx of new developers put a pretty hard market cap on people who "just coded."

Both of these generally have the effect of limiting how much you can expect to get in terms of compensation. And if you live your life expecting your compensation to just go up and to the right, at some point your personal expense (or burn) rate is going to exceed your earning potential, and that is where things get difficult.

As you get older the number of things outside of work that impinge on your working hours gets larger. Perhaps you have family, perhaps you're parents start ailing and need more elder care, perhaps you start ailing and you need more medical care, perhaps you're on your second or third marriage, or perhaps you just like to go camping or sailing or fly gliders on the weekends. The point is, the longer you live, the more your life develops some flavor and nuance and when you felt it was fine to work all day and night and the occasional weekend or holiday, now you really understand the need to keep from burning out.

I think there will always be technical work available at some price, the important bit will be making sure that the price is something that is enough to meet your needs. You can do that by keeping your lifestyle at 60 - 80% of your take home pay. And then if you're pay is cut by 20 - 30% you're not out on the street, your just not saving any money any more. If you do this long enough without a major bump in the road (such as a major medical expense) then at some point you can lose 100% of your income and still be okay in terms of being able to meet your obligations.

To address the two sub-optimal outcomes above you can do two things, one is to work not just on learning new things but on your ability to learn new things. Everyone has a different style of learning, and you have to find yours and figure out how to exploit it. I tend to be someone who learns more deeply by doing rather than by reading. So I when I want to learn about some topic I try to invest time in doing it so that I can understand the challenges and then the forces that make those things challenges in the first place. Everything seems "easy" when you don't really know how it is done, so by doing it you find out why it isn't easy, and for me, that is where the learning is. I know a guy who just loves MOOCs. He's done physics classes and esoteric mathematics classes and loves to work all of the homework problems two or three different ways. I personally have a really hard time on that road :-).

The second is you have to be open to new things in the first place. Having spent a big chunk of time mired in the RPC wars I spend a lot of time debating and understanding different ways to communicate between machines over a network and models to use when doing so. As a result, I reflexively flinch every time someone has a new wonderful way to send messages that solves all the problems of the world. I know, as they will eventually know, that the problem space is like a balloon and you squeeze one place and some other part blows up. So I am tempted to ignore it, knowing how the story comes out in the end. However, by teaching myself to 'score' it differently, I can learn a new network messaging stack with the intent of learning what the people making it were shooting for. And rather than lament their walking into some of the same traps that people have walked into for decades, I try to find how it improves on the things that it is good at with the expectation that those good ideas can be applied across a wide variety of systems. But if you shut yourself out from those things with the famous 'Been there, done that, got the t-shirt' sort of excuse you may miss out on the things on the other side of re-inventing the wheel one more time. So by working on your ability to learn quickly you can mow though the new models and ideas and get on to the good stuff, it is less demotivating.

As for soft skills, I've spent most of my career definitely not wanting to be a manager and then getting stuck in more managerial roles than I would have preferred. Google taught me a surprising amount about management because of their unusual split of responsibilities at the time. It wasn't something I sought to learn (see the being open paragraph :-) because I was afraid to be removed from the ability to get my hands dirty as they say. Switching back to a smaller company where I could try both was really helpful in that regard.