Possibly, but at some point it has to stop, right? Take the extreme example of working 4 hours, one day a week. If you are even marginally interested in what you’re doing, I can’t imagine anyone feeling burned out by that. I just don’t know what the threshold is (and it’s certainly different for different people). A lot of it probably has to do with how busy people’s lives are outside of work, and if they feel like they’re able to manage their lives at least somewhat stress free.