I am generally a pretty hard worker - I've worked in startups and major corporations, in high stress fields under constant time constraints. I could have usually gotten away with doing less I think, but I like to try and learn what I can and I'm miserable if I spend too much time doing nothing at work, so if I have time I go pick up old bugs off the neverending backlog. I've had a non engineering job that basically required me to find something to do for 5 hours of my 8 hour day because I had nothing else to do and it was hell.
That being said, it depends on my burnout. My burnout rate seems to be 3-4 years at a company. I worked hard at one of my previous jobs and climbed actually pretty high up the engineering ladder from a normal non junior engineering position, but got too burnt out with all of the additional responsibility. At that point, I noticed I stopped being as busy, taking more time away from doing basically nonwork things outside of meetings, and becoming a bit apathetic, too much that I was uncomfortable with it and quit because I needed to move on. During that time sometimes I was much less busy than I appeared but it made me feel bad over time.
I've been doing independent ventures lately and got a bit of that fire back but lately feel like I'm falling into the same trap and not being as productive as I'd like, wasting too much time on social media or other timesinks. I really need to kick myself out of this slump, I think I can but really I guess my productivity is linked directly to deadlines which I've been lax on setting for myself lately.
Anyways, long story short I usually don't pretend to be busy unless I'm burnt out, then I quit and do something else.