There is an interesting discussion on the length of work day, especially in academics. I think many academicians look only for productivity and I think advisors only look at the work ethic of the student if the student was being non--productive for a few years. The time that is spent on the work bench is probably less important than the time spent required in thinking about the project.
For the faculty, the key is to plan well and not spend lots of time on long coffee breaks and mostly useless meetings. Of course, in IISc parlance, if the faculty is called hard working, it normally means that (s)he is not very bright !