I disagree. I have read articles like http://lifehacker.com/working-over-40-hours-a-week-makes-you... which claim that over 40 hrs a week on average, for average people, will have lower productivity. I get that sometimes people have to work over 40 hours a week, and then follow it with extended periods of rest. An example is tax accountants. But for continuous producers like executives or engineers imo they are more interested in volume of work completed in 1 year than fastest single week/month.