Hi, 99.3 ATAR here for the 2011 HSC.
In my opinion, I completely frown upon general discussions that debate the tediousness of 'How much study should I be doing per day?' or 'Am I doing enough study to get said mark?'. In reality, the general 'study' times are bogus. Find what works for you - if you feel the need to study 6 hours a day, so be it. If you find you are sufficiently coping with the current workload with 1-3 hrs per day, so be it. Invariably, it is different for all. The effectiveness of study techniques on the other hand is of considerable significance. Some find exercising before sitting down for some study effective. Some enjoy ambient music in the background; others complete and utter silence.
Personally, only on RARE occasion did I ever put in these 5-6 hour days that people typically argue on and on about. It doesn't matter if you're at the bottom or top of your game, it is consistency that is key to success. Consistent revision and rehashing of notes is paramount - at least for most, including myself. This is what I found useful throughout my HSC rollercoster and the few days before the exams. Not trying to sound obnoxious or anything, but I can say that the day before Legal Studies, I had Modern History, so I was very tired. Instead of studying that night and the following early hours of the morning, I was just watching movies. And as it turned out, for Legal Studies (my final exam), turned out to be my most successful subject.
So, I hope this disproves much debate over 'how much' study; more so, 'what works'.