I can give you the run-down on MS-1. It's a bit long, but hopefully it will help explain things
CUSOM divided the class into an "A" and "B" group. Those groups stay the same the whole year. We usually have Anatomy lab M and Th, maybe Tuesday. Each lab the groups switch going first (so you may have 1.5 hours off after lunch to study before lab from 3-5:30 on Monday for example, but then you'll be in the early lab from 1-3:30 on Thursday and be off early then, while the other group is in the lab late). OMM lab on Tuesdays just changes A to B earlier each block, but you may have something else the other 1.5 hour, like an extra Anatomy lab some weeks.
In short, the schedule is HIGHLY variable from block-to-block, week-to-week, and even day-to-day. We got a lot of "embedded" study time first block, but they're packing more Anatomy and other stuff in last block and especially this block. This block we regularly have 3 anatomy labs a week, plus Clinical Skills on Wednesday, usually, etc. Just to be safe pretty much expect to be on campus from 8-5:00, or 5:30 on Wednesdays. You will definitely get out earlier some days, but you never know exactly when that will be. When you get the block schedule you can see which days of the week your A or B group might be out earlier, but even that can change sometimes, although rarely.
The basic upshot is that 8-5:30 is the "official" schedule, and they aren't shy about taking up that time several days a week. You almost always get out at least by 12 or 1 on Fridays, though. This is true for MS-1, you'd have to get some MS-2's to describe their schedule, as I can't speak for them.
Edit:
@polylux , I should have done that, instead of typing all this out. Still brain-drained from the exam, I guess!