I know and worked with a lot of 40+ developers/ DBAs etc. (guess my age :) ) Also know a lot of ex-devs that are now in management or EA roles. I guess that this is normal for other professions as well. Some people like to do/ try other rolles or careers so it is not a big surprise that people with long careers don't always do the same stuff that they did when they started out.

I guess it is also a good thing, when I started as a developer most managers didn't know anything about coding/ architecture etc. Now a lot of companies are specifically looking for managers with an engineering background

so no careers don't die at 35, but people choose to do different things and more people are starting dev careers than back in the day