How about: way more than I thought I would?
I have a system for my M.A. exams for my grad students. I developed this system to try to balance student interests with me not going completely insane trying to make sure I knew all the material that they'd covered for their exams. I haven't been in the biz long enough to have an eight-page bibliography from diverse medieval stuff topics from memory or in my notes already, and since I'm the only medievalist, I've got to be able to cover students interested in stuff all over the continent, for the entire thousand-year period.
Here's how it works: Students taking a M.A. exam with me have to read about 45-50 items, spread out over 5 different subtopics. I have a list of about a dozen topics that I've got reading lists ready to go for.
But, here's the deal: if there's something they really, really want to explore, and it's not on my list, they can design a field of their own. They come up with the topic and a preliminary reading list; I tinker with the list to make sure it works, and off we go.
What this means is that, for most students, I end up reading up on a field that's totally new to me. Sometimes I couldn't care less about the field. Anglo-Norman institutions? Do. Not. Care. But I read them, and I try to design a question. But sometimes, it's pretty interesting.
Which is a long way to say that this month, I'll be reading a whole heck of a lot on Islamic, Norman, Angevin, and Aragonese Sicily. And I think this is actually going to be one of those reading lists that ends up being a lot of fun.