I think I said to myself I was going to have a break until NYE, but I kinda got into holiday mode and slacked off way more than i should have. I was away for two weeks in Jan also, so I didn't do any school work in mid Jan. I think the main thing I focused on doing was my English portfolio for AoS as it was like a 25% assessment.
My advice is set specific goals for your study these hols THAT ARE REALISTIC but don't go too hard out at this point. I set massive lofty goals that weren't realistic, which meant they didn't get done. You don't want to be burnt out come Trials time or worst, the actual HSC (I had little motivation left for the actual HSC, the time when you want to be the most focused). I think the problem with my break is I got out of the habit, I think the best would be a little each day if you want to do some work, consolidate things from the 1st term and perhaps look ahead (i.e read your English texts or have a sticky at next module). But it's not a time based thing, it's better to do an hour of focused study in the morning with a goal(Like do these 10 maths questions) than to leaf through your Mod His folder for a few hours aimlessly.
Point is, there's plenty of time in the HSC year to do all the work you want to get done and more, I was away for 2 weeks in summer holidays, and most school time/most of the winter holidays in June/July and I still had enough time to get my work done with many extracurriculars and still have time in the year to slack off on occasion and watch a season of 30 Rock/procrastinate. It's all about balance and the long term effort