I have been working without rest for a year on a project (http://www.stremor.com) that has had huge amounts of progress. It pays well enough, I like the people I work with, we have achieved great things, and we have gotten recognition. So by all these measures I should have no burn out.
I have been burned out several times. You can’t do genius level work 40 hours a week for 52 weeks and not burn out. The Addiction to progress I have had me doing 80 and 100 hour weeks. I was burning my self out. Not because my needs weren’t met, but because the brain just can’t do that much work for that long.
I would sleep through an entire weekend after 2 weeks of 100 hours. But the addiction to progress and the excitement of the work meant that I didn’t want to “go play”.
What it really comes down to is people have limits. Those limits are additive. If you are at 40% of your financial stress limit, and 40% of your relationship stress limit, and 40% of your Micro-Manager driving you batty limit, then you are at 120% of your limits. And you can run for a while at over 100% but not indefinitely.
Even when all my Career, financial, physical, sexual, and other limits are at 5% if my Hours of intense concentration limit has been hit I will burn out. And so will employees.
The task of a good manager is to run an employee up to the point of the Mental limits and make sure all those other limits are at 5% so they can maximize the employee output. Every time you push the employee at 150% for 2 days, you need to let them recover at 75% for 4 days.
Burn out isn’t a bad thing as long as you can refuel and keep going. It is about managing the sprints, and preventing the burn out from causing failures.