Meanwhile, the consensus on various HSC forums seem to be around 1200 words MAX.
Wait, there are forums
besides AN?
Ahahaha, in seriousness, to throw in my two cents on top of the awesome answer from owidjaja. Any student who can write 1400 words in 40 minutes without rote learning an essay, needs to be an extremely effective English student. It's not that writing that much makes them effective, it's that they write that much because they are effective - It's important to get that causality right.
With that in mind, we recognise that it's not that the longer essays that do better. The better writers and better arguers do better, and it also so happens that they also tend to write more. Should YOU write more? Definitely not - The ideal number of words in an essay is however many you need to argue your point effectively. That's different for everyone - I've seen 20/20's well under 1000, I've equally seen 20/20's hovering at the 1500 word mark. But it's about efficiency - The aim is to write about exactly as much as you need to get your ideal score, then move on!
Lots of factors here - But anyway, all about the advice above, if you can't write it in the time limit, then it needs to be shortened! If you can, then you're gold. Simple as that - But remember you want time to adapt it to questions on the fly