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.