We get 9 weeks from the end of second year to the start of third year.
The first four weeks are actually a course called "integrated problems," which is a board review type course in which you go over interdisciplinary cases to tie together all the subjects from the first two years. It only runs from 9-11 or 9-12, and there are no tests, and I've heard it can be very helpful. The downside is that it is mandatory, so the people who'd rather just study on their own find that irritating.
The next 5 weeks are your own and you can take the test any time you want during those 5 weeks. Any time between when you take the test and when third year starts is vacation time. Most people I know take between 3 and 4 weeks, leaving at least a week of vacation. You don't have to take the test in Pittsburgh either, and many people go home over those 5 weeks.
The 9 weeks Pitt gives is on the high end for most schools, though people have mixed feeling about the integrated problems aspect. Even if you don't like it though, its only 2-3 hours/day and you can spend the rest of the day studying. I've heard that people do very well on the boards here, though I don't have any numbers to back that up.