It’s probably better thought of as a first-stage career: 15 years as a pure techie is probably as far as you want to take it. By then you should have transitioned well into management or marketing—or be gearing up to learn a new profession.
But that’s as it should be for many more manual laborers as well as teachers, police and firemen, etc.. We can’t be expecting to be retiring in our 40’s—and then living off of some grand pension for twice as long as we ever worked.
Our brains and brawn are best used early, in a first-stage career.