Keep in mind that they're marking essays for the biggest VCE subject, so if you can produce a short and sweet piece, they'll definitely appreciate it!
You can make your pieces 500 or 1500 words long, it doesn't matter at all. They refer to their assessment criteria (
http://www.vcaa.vic.edu.au/Documents/exams/english/2009Eng-crit-descriptors-V2.pdf) when they read every single essay, and if you can satisfy the requirements to get a 10 within 500 words, you'll get it, simple as that.
The exam is designed to be done within 3 hours, so that's why you hear recommendations of around 800 words, because that's the amount of words you'll probably need to create an "insightful" and "sophisticated" piece within the constraints of a 3 hour exam.
You should definitely keep your essays concise I believe. If you're going to try to use filler words to extend the length of your essay, the examiners will pick up on it, and you'll most likely lose marks for it.
So pretty much, quality > quantity, like everyone says haha!
