Trust me in making as much notes as you can in the holidays. Of course pace yourself to do a bit everyday and use this time to have fun. If you think about it and plan your entire day really well, you can have fun during the day with friends, then at night say 6pm-11pm, you can pull a solid 5 hours (which I assume people do during the school term anyways). If you are able to do this everyday with a few days of no work, you will easily be able to make notes for all subjects beyond the HY + practice sufficient maths (~1hrs a day minimum). Go hard or go home. You have 24 hours in a day, no school to waste your time in your holidays, get that time management game on
Essentially you will not regret this as whatever you don't do now, you will do later. Everyone has their periodic phases of absolute ceebness where they are just inefficient and can't be bothered doing anything. By doing things early, not only can you consolidate knowledge during classes, you are able to take a breather when you are feeling 'burnt out'.
Having what people call 'burnt out' or 'HSCeebs' only exacerbates a hopeless situation where they aren't prepared and can't be bothered working. This is mainly because they are overwhelmed by the sheer amount of work they have to do. If a major bulk is already done, you are more inclined and more motivated to keep nudging on.
Another reason of doing a lot of things in the summer holidays is that whilst you may be feeling crap during your break, trust me that you will be the one feeling relaxed and organised when it comes to term 2 - term 3 exams/trials where it is essentially exam after exam. You will no longer have time to write notes and it is just a viscious cycle of unpreparedness where you are trying to tackle exams while learning ahead or keeping on top of things, a very strenuous and difficult task.
tl;dr DO WORK DURING HOLIDAYS, HAVE A TO-DO-LIST, PACE YOURSELF, YOU WILL NOT REGRET IT, WHATEVER YOU DON'T DO NOW, YOU WILL DO LATER
