>Does that mean that from just working extremely hard, you can never (very likely) get a burnout? That would be big news.

The research suggests that burnout is a lot less likely if you enjoy your job and have sufficient support (see the Demands-Resources model of burnout).

From research into the brain (see Boksem 2008, and Noakes 2012) there appear to be areas in the brain dedicated to calculating the costs vs benefits of performing activities. Some of the inputs to this system are emotion-based, but others are physiological (e.g. sleep, tissue damage, etc). You can override your brain's fatigue/tiredness signals, but if you do that long-term then burnout will still likely occur.

An interesting factoid is that fatigue itself is actually an itself (see Noakes' reviews). So what will likely happen if you continue working hard 16 hour days is that your brain will say "enough is enough" at some point, and you will start to feel negative emotions towards your work even though you previously enjoyed it (and even though consciously you still want to do it).

>By the way, I've heard that sleeping a lot (like 10 hours per night minimum) helps with burnout; not sure if it is universally true.

Well, it will certainly help if you are suffering from short-term burnout, or to avoid burnout in the first place. Sleep is definitely one of the factors that the brain uses in determining fatigue/burnout.

> Does that mean that from just working extremely hard, you can never (very likely) get a burnout?

Dashrath Manjhi ran away from his home at a young age and worked at Dhanbad's coal mines. He returned to his village and married Phalguni Devi. While crossing Gehlour hills to bring him lunch, she slipped and seriously injured herself, which eventually led to her death. Manjhi was deeply disturbed and that very night decided to carve a path through the Gehlour hills so that his village could have easier access to medical attention. He carved a path 360-feet-long (110 m), 25-feet-deep (7.6 m) in places and 30-feet-wide (9.1 m) to form a road through the rocks in Gehlour hill.

https://en.wikipedia.org/wiki/Dashrath_Manjhi

Not a statistical argument (which your words suggest you expected), but I think it agrees with the spirit of the article - you can find motivation for truly crazy stunts if you focus on obtaining future good emotions instead of avoiding present bad emotions. Working to avoid losing the rat race is a burnout-prone kind of motivation, for example.

Just to add to my previous comment: there seem to be a few people who can achieve continual high levels of work output on about 4 hours of sleep without burning out. I suspect this is a combination of genetics and being highly in control of -- and motivated by -- the work (e.g. owning the company). Perhaps it is a kind of long-term mild hypomania.

The problem is when these people sometimes think that their employees should be able to handle the same workload, which then inevitably leads to burnout.