Might depend upon the school. My schools strats board review after exams end in April. They used to just have Kaplan come in and do it, but they stopped that. Now, they picked the best Kaplan instructor and use some faculty folks as well. After two weeks of that they have a "mandatory" week or two for students with grades of 75 or less. They buy us some review books, buy us access to Q-bank and Kaplan videos. Honestly, I don't know how anyone would really need more than that. Still, some folks do.
As for the OMM part of it, every test we ever took over two years was cumulative. We had big exams at the end of each year too. I never reviewed OMM because we were reviewing it constantly for two years.