do whatever feels good for you! if you want to focus on bigger chunks then go for alternative weeks, although personally i would alternate days (or every couple). try not to panic too much, and don't over-cram or you'll forget stuff. set a sensible schedule, a few hours a day maybe (depending on extra-curriculars, homework and other subjects) and try to vary your revision to retain as much as you can, and to feel what's right for you. i'd advise to do some practice timed essays/ creative writing, just so you get used to the time limit and setting them out.