If you're forcing yourself to stay away, then you're not productively taking in any information anyways. On top of that, if the exam is the next day then you're going to be legit brain dead in the exam. Simple things that you probably would've remembered the before might slip your brain. Another thing besides the syllabus content, you will lose your ability to eloquently and succinctly write your responses too and that probably has an even bigger impact on screwing up your marks (esp. for English). The only time I say it's ok to sacrifice sleep to study/work is assignments because you can freely zone out the next day.
Unpopular opinion but I believe it depends on the individual.
I have always been able to function properly on 4-5 hours on sleep. I also prefer to study at night so my 'golden hours' are 9pm–2am. During this time frame, I can study at maximum efficiency without any breaks and it worked really well for me during the HSC. On the other hand, I had friends going to bed at 9pm no matter what and they also did very well.
Maybe you can try both and see which works the best for you.
I agree to a certain extent, but also IMO people who are "night studiers", (from personal experience at least) that's placebo. I would procrastinate the entire afternoon away and get really down to business after dinner, but that was mainly because of this increased pressure that I was like "Oh crap, the day has just slipped by I better do something." That meant that it wasn't necessarily that I couldn't study in the arvo, it was just that I didn't feel the pressure until it was almost bedtime and then my efficiency levels would go up.