You will be hearing this advice time and time again, and that is, it is not about the quantity of the hours you study, but the quality of your study time-so how much you have understand/learnt from each studying session. The number of hours you study in the upcoming summer holidays will depend on three main factors:
1)whether you are going overseas/travel, and if so, for how long and any other possible tutoring/extracurricular/casual work you may be engaging in over the holidays
2)The main goal of your study during the holidays-whether it is to catch up on content/to revise on content learnt/to learn content ahead of class-although you may well be doing more than one of these at once, just consider one which is your main purpose-and consider how much time you are willing to devote/think will need to be devoted to achieve that purpose-based on your own study efficiency and methods
3)Whether you intend to focus on all of your subjects in the holidays or are intending to focus on only a few
To maximise your HSC school holidays- you should strive to achieve the following objectives:
1)To truly relax after a tiring school term-you should go out with your friends-particularly over the summer holidays where you have a longer period of rest, leave 2-3 days a week to relaxation and fun-do things you enjoy, it is very important to re-energise and re-vitalise yourself so that you are highly motivated for term 1, as well as establishing a healthy daily routine because a healthy body will mean a higher capacity to cope with the stresses of HSC-(making sure you have good physical and psychological health is a vital key to achieving a high ATAR)
2)To evaluate over your previous term's performance and establish short term and long term goals and strategies on how you could improve, establish more efficient/effective study habits-experiment with new study methods and routine, organize your room/study file/study schedule if you haven't done so-and enforcing regular self-discipline and independent learning in your study.
3)To revise over all content learnt(because they will be examined in trials and HSC-so more regular revision is better than revising the whole year's worth of content at the end of the year) and learn new content-preferably at least one term ahead of the school, but make sure you do questions/practice essays/creative to be able to utilise both past and new content effectively-highlight any parts you don't understand to ask the teacher during next term
4)To finish exam preparations for assessments that are established early next term, i.e. perhaps your half-yearlies for English, and to finish assignments due early next term as well as any homework allocated by your subject teachers
One last word of advice: every individual is uniquely different, so your school's quantitative recommendation of your study hours just expresses your school's high expectations of the cohort to keep studying hard in the holidays, it may not have been established so people will follow it literally, but just to remind people to retain that HSC motivation/concentration over an unsupervised period: i.e. you don't have teachers urging about you handing in homework and assignments. It is excellent that you have thought about the possibilities of burning out-and I truly urge you to relax sufficiently for the holidays, and a big part of that is to not sleep too late-you should establish a regular sleeping pattern to maintain good health as well as do a regular amount of exercise.
Make sure you are studying at hours optimal to your alertness and concentration, and establish an objective for each study session and strive to achieve it, and upon achievement of that objective, you should reward yourself-either with free time, a snack, or something else. Strive to investigate more deeply into the topics you are studying, to develop a greater interest in them, and to consistently work hard. 6 hours might sound like a lot, but if you truly love your subjects, the time will past really quickly. Time is a luxury in the HSC, so make sure you are planning your holidays well before hand and using it very wisely-in a way that you will not be regretting. And for English, you should strive to read all your prescribed text and perhaps start finding related text for your relevant modules.
Overall, you should be aiming for happiness, consistency, persistence and balance in your holiday study schedule. Hope my advice helps and I wish you all the best for your HSC year