For about the last 2 years, I have taken to making my travel bookings very late in the planning process. I used to plan my trips quite meticulously, knowing my travel dates well in advance and looking for the cheapest airfare for at least a couple weeks.
Now, it's much more, not quite spontaneous, but certainly more haphazard. I think the transition occurred when I started working in Hungary for a couple different reasons. It's a mix of trip locale, people I'm going with or seeing, cost, and my own work responsibilities. That last one is pretty key. I'm going home soon, but I've twice postponed the trip by a couple days. More responsibility here makes it harder to just pack up and go. Plus, and I'm not saying this takes a lot of time, but actually booking tickets on a slow network connection means making time and free time is hard to scrounge up. But hey, it's done. I'll be back soon enough.