When and how to revise for AS level exams?Watch
Start making notes now. It'll save you time doing it later. While making notes you'll retain some of the stuff you wrote so you'll be doing some light revision. I'd say 6-8 weeks before you'll start going full on but you can start earlier if you want
You have enough time, but don't be complacent. You don't need to work at full capacity right now, but the work you do now will matter.