Last semester, for various reasons, I ended up "double-teaching", offering both my undergraduate algorithms class and my graduate network algorithms class. The disadvantage of double-teaching is that it take a lot of time and, in my experience, is very tiring -- especially when you teach the classes back-to-back, as I did. It's not apparently recommended practice here, as there's a clear preference for teaching one class a semester. I can certainly see why -- it's good to have reasons for faculty to come in and interact, both with students and other faculty, and a class is an anchor for all sorts of interaction. But a lot of our faculty were on sabbatical in the spring last year, so I was able to do it.
The reward for the work last semester is that I'm not teaching this semester. I still find I'm coming in, in part because there's a lot of administrative things that have to get done (especially the first few weeks of the semester), and in part because it's often not productive to work at home with a small toddler there. But I'm enjoying having the time available that comes from not having to teach.
The question is what to do with that time. I've had a good research summer, including finishing off a number of journal versions that had been lying around, and I certainly could just keep going forward on a number of research projects. But it feels like I've been given a few months of opportunity, and I should find a way to use it. I have a couple of ideas for books, and I feel like (after I finish off a few more dangling research projects) I should motivate myself to start one of those. I know a book is a big project, so even with this opportunity it will take some mental discipline to get started.
For those who are faculty, what would you do with a semester off of teaching (where you can't go away on sabbatical)? Anyone have any suggestions on what to do with the gift of time?