It absolutely is unhelpful in anything more than short bursts. It is very odd how obsessed she seems with hours-worked.

Mayer is someone who proclaims to believe in the power of data. I'm curious then what data she has to back her views on crunch==maximization of value creation. Most of the data I've seen says the opposite. It seems Mayer may be letting her anecdotal experience in the early days of Google trump data here. (A it's also possible that anyone, including Mayer, can have misperceived or misattributed the importance of sustained crunch in those days or its causative effect on success.)