How many hours a week should academics work?

Published on 14th January in the Times Higher, David Matthews discusses how research casts doubt on whether working long hours is a productive work routine.

‘How many hours do you work in a week? Many academics feel overworked and exhausted by their jobs. But there is little evidence that long hours lead to better results, while some research suggests that they may even be counterproductive………………………………. At parties, Michel is constantly asked what she has published recently. Working at the weekend is a “badge of honour” for academics, she says. And because knowledge workers, be they academics or bankers, are constantly competing against each other, their hours keep ratcheting up’.

Although not discussed in this article the problems associated with working long hours would also apply to PhD students.  How many hours do you work in a week?  Would you be more productive if you changed your work routine?