Start now, making notes on everything you need to know. I find that making notes from a revision guide is beneficial as it means that I only have a few pages to revise for each exam, and writing of them helps you remember a lot of it.
I'm going to finish my notes this month, then do past papers until a few days until the exam, then I'll just read through them multiple times just before the exam.
I would say 1-2 hours per night is fine in Feb/March, and as said above, take days off. We still have a long time left.