Does Sustainable Pace mean a 40 hour week?

It is travel day and I have some extra time to catch up on my RSS feeds. On InfoQ I came across this:

InfoQ Personalized Feed for Stephan Schwab in Does Sustainable Pace mean a 40 hour week?:
Sustainable Pace is a well known XP practice however, different people relate to it in different ways. Could an Agile team increase its sustainable pace by working longer? An interesting discussion on the Scrum Development group tries to debate the correlation between the number of work hours per week and sustainable pace.

Interesting thought but probably completely futile and towards the wrong direction. Software Developers are not anywhere similar to machines because they are humans - not resources, as many misguided project managers, and probably many managers in general, perceive these talented people. You cannot increase the input and get more output.

On any team you need to leave room for learning. Without learning there is no improvement in productivity or quality or anything else. Skipping the learning means stagnation. In a profession such as software development stopping to learn is dangerous and will get the company and the individual developer into trouble in the near future.

So... Maybe the right question would be to ask how much time out of the regular work week should be devoted to learning, which is not related to the problem being solved in the current project. What the software development profession at large is in bitter need of is a much more elevated level of skills and knowledge and that includes developers and those who manage them.