I firmly believe that most academics are work-a-holics. It is not uncommon to see at least a few of my colleagues working in the office on Saturday or Sunday to "catch up" on a few things here or there. I seem to find myself there frequently.
When I first started my career as a professor, I used to tell students that being a junior faculty member is much like being a graduate student in terms of the hours, but that one gets paid a bit more. This type of job is one in which you can carry around a task list and think about all there is to do 24/7. Rarely is there downtime. In fact, if you want downtime, you must consciously make an effort to walk away from your work and relax. For me, exercise seems to be the first thing that I lose when my task list lengthens. Each year, I pledge to do better. So far, the intent has outdone the reality.
Of course, I think a lot of academics love what they do. We may grumble occasionally and look really stressed out as we get buried in the piles of paper, but despite all the multi-tasking, there are very few other types of jobs in which one can have as much opportunity to grow and learn.