I was fortunate enough to pivot from Chemistry PhD (which I completed) to a career at Microsoft that has provided me with more than enough financial security to fund an adventure like this when I do decide to retire. While I may not be typical, I do use skills (though not specific knowledge) from my PhD all the time in my day job - mostly around communications both written and oral. The act of writing my thesis and papers really taught me the value of being able to communicate technical information clearly to a technical audience.

I think that the structure of pursuing research would be a great way to avoid losing a "sense of purpose" that I fear might await me when I do decide to retire. The tricky part of this is finding the right advisor and the right project in the right field.