Tips from an IB dude who took the exams last year. I, like many of you, had no days off except for that one tiny weekend. One thing I highly recommend for the cramped people: know everything. BUT...on paper 3 days for sciences, just cram them the night before (provided you have an excellent understanding beforehand). Paper 3s for sciences are repetitive, straight-forward syllabus questions. Especially for physics and chemistry.
For those doing history as well, study LOADS for it. I did IB exams last year and I had a cramped workload until the 13th like a lot of you have. For history-- you need to revise very strategically and in a lot of depth. If you aren't prepared for something like Paper 3, your marks are going to go down. So yes...I definitely found history to be the hardest set of exams simply because I spent so much time on physics the same day. My real score in history went down 2 points from my predicted simply because of physics. So yes, know paper 3 of physics well beforehand and just ignore it until the night before.
As well, make sure you don't neglect a science. I neglected chemistry...and paper 2 was the craziest thing I have ever come across for the North American time zone. It was the hardest exam I have ever done for SL. I once again let physics control my life and neglected chemistry-- and the physics exam was one of the easiest I have ever come across. Bah...unfortunate. So yes...keep both sciences together if you are doing two sciences. Good luck, everyone!