My observation has been that people working more than 8 hours a day for more than a week only overproduce for a very short time. 16 hour work days general degenerate into spending most of the early day fixing bugs from the day before, tiring you out so when you get those 'fixed' you spend the rest of the day introducing 'new' bugs, then repeat the next day.

There are certainly some companies with a culture of overwork, but the people that actually produce the most are not always the ones who work 16 hour days. I have worked with a lot of people who believe working hard is 'good enough', but I'd never hire them. You have to be able to actually produce something, or you're wasting your time.

It's a tough balance to find sometimes.