I guess the easy answer is that it all depends on where you go to school. Where I go, we have the Navy Battalion, made up of Navy Companies, with a separate Marine Platoon (I assume it's like that most places). Anyway, we have Battalion events on Tuesday and Thursday mornings (0600 and 0530). We have company events on Wednesday or Thursday afternoons (1600 or 1700). We also have Marine Plt PT Monday/Wednesday/Friday at 0545. Not to mention Semper Fi society meetings Wednesday at 1815. Plus, during football season, we work at all the football games (Friday night and all day Saturday)....
Write all that down on a weekly schedule, add in 15-18 hours of classes, plus work, plus family/friend time, plus study time, plus fun time...you can probably see where that is going. Anyway, that's what you possibly face if you go NROTC (Marine Option). If you go PLC, you stand the chance of not punishing yourself physically enough (or in the basic skills department) to really be ready for OCS. We do a lot of crap. But I feel pretty sure I'm ready for OCS, provided I don't get injured...again!
Good luck!