A couple of times in the last few weeks, I've come across stories about productivity and amount of time worked. This won't come as a surprise to anyone who's been reading posts here, but I don't believe that working 16 hours a day yields twice the "stuff" that working 8 hours a day does.
For one thing, measuring hours worked is a lazy and inaccurate shorthand used by bad managers. As the "Evil HR Lady" writes, if somebody isn't getting their work done, the issue isn't that they're not working enough hours, it's that they're not getting their work done. The hours are a distracting issue.
At the extreme of this line of thinking is the "results-only workplace" and unlimited, untracked vacation time. I'd have to do a lot more reading to do before buying into that, but I do think there's not a ton of difference between the output of 45 and 50 hours of work in a week but that there's a large difference in quality of life, employee happiness, and burnout.
There was also this New York Times column that observes that "an unfortunate reality that efficiency often goes unrewarded in the workplace." That came from Robert Pozen, author of "Extreme Productivity: Boost Your Results, Reduce Your Hours."
The overwhelming message: Get your stuff done. Then quit staring at your email. Come back to work recharged and ready to be awesome.