Guys, 3-4 hours is more than adequate per night during normal periods.
My main advice would be
-get your assignments over and done with asap
-it isn't about studying 10 hrs the day about the exam, it's about studying consistently.
-Do your creative AOS essay during the xmas holidays, you won't regret this
-keep upto date with notes, the further you let it go the less likely you'll ever catch up
-do past papers throughout the year, not just before the exam. Once you finish a topic do some questions to consolidate your knowledge
Goodluck to all, remember the hsc isn't the end of the world though