I have never been burned out, but I think I would have been. I did a couple stints at various places (non dev work) where I was pretty excited to continue working and get higher in the org. Fortunately for me they were co-ops which ended and allowed me to see that, retrospectively, they kind of sucked, were not especially fruitful career tracks, and would have ground me down after a year or so. It’s really hard to check yourself while engaged and working on something.