Well, it's a marathon, not a sprint. A CEO that isn't taking care of him/herself isn't taking the long view. Sacrificing your health and not making time for thinking big thoughts is a bad way to lead a company.
There is a small subset of people who are able to work 80+ hours weeks without end (and are also intelligent, conscientious etc.). I think a significant portion of highly successful people belong to this group.
There's a big difference between working super hard and working so hard that your health fails. If you aren't pushing 60 hours a week, you aren't even trying. At a startup, so many things are out of your control, but one thing you can control is working hard. All that time and effort, and failing because some other company out-hustled you is the worst reason to fail of all.
Burn-out is a thing. A CEO that isn't making time for focussed reflection can very easily get stuck in 24x7 fire-fighting mode. A tired, burnt-out CEO won't be finding creative solutions to problems.
