Extremely impressive but is it really sustainable in the long run? I personally do not think that working 16hr days is good for you in the long run. It is not healthy.

What use is he if he gets burned out in a year or two? Not much I would wager. Sure one might argue that this pattern of long working hours is crucial in the first few years of a company. The question if he does so much more in 16 hours than he could have done in say ten or twelve? I doubt you can remain very efficient 16 hours per day.