We have mid-semester breaks (not necessarily co-inciding with the middle of semester), and course co-ordinators really use their own discretion about whether they want something submitted before or after it. In PolSci courses, we tended to have our major essay for the semester due right after the mid-semester break, and the major exam at the end of the semester. Occasionally we got lucky and they did the History method of two major essays and no exam, with one due roughly halfway through semester (not necessarily coinciding with the mid-semester break) and the other at the end.