People always joke about the whole, 'sleep is for the week', and I'll admit I used to say that in year 11 - but trust me, you do not want to be missing out on sleep. You're an idiot if you continually sacrifice your sleep to do work. The longer hours of study you are doing, and the later into night you are eating out of your sleep, the faster your concentration and quality of work deteriorates, and the less you retain. Essentially, it's time wasted that could be spent sleeping. Work it out. Get what you need to do within the day time/evening. Maybe you could wake up a bit earlier to study?
I think All-nighters are a no-no, unless you don't plan to listen in class. Even then, it confuses your body clock and suddenly you're going to be sleepy all day everyday until you start sleeping normally again. From experience, 2 drowsy days follow every all-nighter. That's also two days lost from efficient study you could've been doing.
Also, I would recommend you to keep your social life - it's kind of an outlet for stress, calm you down and a source or some other fun outside of classroom. On a personal account, I did become a bit crazy (lol) during year 11 and 12 with the lack of sleep and a balanced lifestyle. Consequences were that my HSC results definitely did not reflect my capabilities nor efforts throughout the year (97.85 ATAR). I just kept forgetting things that I had learnt over and over again because of the HSC lifestyle choices that I made - sleep deprivation etc.
Hence, I'd definitely recommend you to sleep as many hours as is necessary for you. Second, it might be time for you to up your game in study, which might be an additional 2 hours over what you're doing now, or whatever it might be when you figure it out. Perhaps you might have a FEW late nights, but don't push it. You don't want it to become an unhealthy habit. As for study specifically - find out what you need to completely, and try to write goals for each day, and track your performance so you won't be like 'oh my god I haven't studied for anything' one week before your half yearlies.
Edit. I would not recommend cramming, because during that time all the information you revise/learn is stored as 'short-term', and you'll end up having to learn/revise it all over again after the exams. It's not very efficient. Take it easy, and ask lots of questions if you need help, but don't wait until last minute. Cramming should be the absolute last resort.
Good luck.