Hours per day

• Back some 25 or nigh-on 30 years ago I worked part-time in an office. One of the first things my dad pointed out was that when you work part time you're working all the time you're there. If you're a full-timer you're making phone-calls to your spouse at home, you're running off with your car to the DMV to get it inspected, you're ordering lunch. But me, as a part-timer, I was sitting in front of a computer (doing what turned out to be completely useless data entry) all four hours of my day.

• The thing I've noticed about having multiple part-time editors is that they edit quickly. They get a LOT of work done in 4 hours or so. Sure, they're only maybe coming in a couple days a week, but they party hard on getting work done.

• Let's take a look at the abstract from the International Game Developer's Association's paper on "Crunch time" vs the 40-hour work week: 

Executive Summary

When used long-term, Crunch Mode slows development and creates more bugs when compared with 40-hour weeks.

More than a century of studies show that long-term useful worker output is maximized near a five-day, 40-hour workweek. Productivity drops immediately upon starting overtime and continues to drop until, at approximately eight 60-hour weeks, the total work done is the same as what would have been done in eight 40-hour weeks.

In the short term, working over 21 hours continuously is equivalent to being legally drunk. Longer periods of continuous work drastically reduce cognitive function and increase the chance of catastrophic error. In both the short- and long-term, reducing sleep hours as little as one hour nightly can result in a severe decrease in cognitive ability, sometimes without workers perceiving the decrease.

That's all I got. There seems to be little modern data out there.