Hours worked in research vs teaching professorships
Looks like Jacobs and Winslow (2004) address this issue.

"the average workweek for full-time faculty exceeds fifty hours. These long workweeks are characteristic of all groups of faculty, irrespective of rank and institutional type. In other words, assistant, associate, and full professors all work in excess of fifty hours per week, as do faculty at research, liberal arts, and comprehensive institutions."

Jacobs, J. A., &amp; Winslow, S. E. (2004). Overworked faculty: Job stresses and family demands. The Annals of the American Academy of Political and Social Science, 596(1), 104-129.