Friend of mine has just completed a Fine Art degree. She was often given something like half a semester's notice of brief and final submission/crit date, and three or four days before that date her chief concern wasn't so much getting it finished as getting it into the gallery and on display without damaging it.
Mollykins, we all like as much time as we can possibly get to prepare for exams and a whole host of other events. But we don't always get it and yes, we have to put a fair amount of our own time into things that we'd really rather not. But life's like that, I'm afraid, all the way up to the end.
As Sprinter and I have both said, try to spend what time you have actually doing the prep rather than whinging about it. If you love the subject, you'll not mind putting 'extra' time into it anyway, and if you hate it, then it doesn't make much difference.