I will turn 64 this year. Started programming in 1974, employed since 1979. I never moved into management for long, I don’t like it.
If you want to stay employable master the fundamentals. Despite all the surface churn software development changed very little during my career. I still use Unix (Linux), vi (vim), SQL, and C-family languages every day. And I use lots of newer stuff too.
Don’t focus on frameworks or other fads and fashions. You may have to learn them but don’t think “React developer” describes a long-term skill you can rest on.
Make as many friends and contacts as you can at places you work. Not just fellow nerds — I have contacts who run companies, work as CFOs and logistics managers, have senior positions at Silicon Valley companies, banks, government. A good network of people who respect you will prove invaluable. Treat your work colleagues like gold, help them get jobs, stay in touch.
I don’t have the energy of a 20-something anymore, I can’t work 16 hours on pizza and beer like I used to. But I don’t need to burn so hot, I usually already know how to solve the problem because I’ve seen it ten times already.