I think you've already made a really important step in recognising that burning out from studying is indeed a prevalent thing, and that you're actively trying to prevent it! I say this because I burnt out last year (and just before exam time of all times) and at the early stage of the year I had very little idea that it was actually possible to physically hurt from stress. So, I have a lot of respect for you. In regards to study burnout, I think that prevention is far better than cure.

I wholeheartedly agree with the advice you've already been given. By all means, Year 12 is a marathon and not a sprint and thus it's vital that you give yourself breaks. In addition to what's already been said, I think it's helpful to identify the times in the day when you work best/have the most energy (so for me, I was always the most productive at around 5:30pm after going for a 30 minute walk/jog) and, if you can, use that time to do schoolwork or study. By utilising this time you're likely to be more productive and efficient, giving you more time to unwind and do the other things you enjoy. Furthermore, give yourself time between studying and going to bed to do something leisurely each night.
Lastly (and this is something I cannot stress enough), but if you do notice a change within yourself and think you might be starting to burnout a little,
please talk to a teacher you trust. I did this, and I honestly think it was the best thing I could've done for myself. It may feel like it sometimes when your SACs begin to fall on the same dates or you feel like you have a never-ending pile of homework, but your teachers aren't working against you. When I was starting to notice that something was off and I was feeling like I was burning out, I mentioned it to my favourite teacher and he actually helped me out immensely... even up until the day ATARs were released. Having your teachers aware that you are feeling a bit overwhelmed makes the world of difference, I promise you. It doesn't have to stop there either, if you feel like you're struggling with your stress do talk to someone (this can be a healthcare professional) too. Around exam time I asked my GP for advice to deal with stress and burning out, and it helped me tremendously. You're never alone on this and there's always people who are willing to help you out.
