Math Professors -- On average, how many hours per week do you think is required to gain tenure?
I've said this in another thread: if you are outstanding and efficient, you can do the work required in a 40-hour workweek.  

An electrical engineering professor I know got through graduate school at MIT working 9-5 days with a wife and three kids (all born during school), and he was a shoo-in for tenure (and received it).  But, when he was at work, he was at work--I never once saw him out of work-mode during the regular day, and he put us graduate students to shame with his work ethic.  His efficiency and focus puts him over the top.  I know I couldn't be that efficient every day, but he makes it a priority to do the best he can at his job (which he loves) and also for his family, and he's figured out how to do it within the confines of a typical working week.  Granted, he is also extremely smart, but I believe his efficiency is as much responsible for his success as his brains.