But that's the point. Burnout is not one of those things about the people's opinion is the fact. People often are completely wrong about they being stressed at the exact moment you ask them, and burnout is about the kind of long-term experience that people are really bad at measuring.

Besides, even "do you like chocolate" is a very bad question to ask if you want to take any actionable conclusion from your data, or even if you want to sum your anecdotes up. You can't go asking people "do you like chocolate" and expect to know how much chocolate they will decide to eat, for example.