At least, that's my own philosophy. Personally I abhor the idea of prepared responses and am yet to meet an elite elite English student (upwards of 46) who has used that tactic.
Haha, the MHS dux of 2009 (50 english) memorised for section B too I think the dux of 2011 did the same as well.
It's actually a LOT more common that you think
One of the guys who got 50 last year told me to write themed paragraphs for R&R and Context and essentially memorise them. Then during the exam, all you have to do is tweak them to the topics. The good thing about preparing some themed paragraphs is that you already know what you're going to write is good, and that gives you a higher confidence than somebody who's kinda making it up on the spot. Of course, there is a risk that you won't be able to adapt to the prompt enough, so be careful.
I'm not sure if I memorising paragraphs word-for-word would really help, but it can stop you from "freezing" in the middle of the exam. It can also help you with speed, you can literally write your context essay and finish very comfortably if you memorise the entire thing.
For my Henry IV practise essays, I basically just tweaked my paragraphs according to the prompt and my teacher said it worked really outstandingly. I wrote a summary of all my themed paragraphs (so main points and quotes) the day before the SAC, highlighted and colour-coded them, and yeah I was able to come up with lots of flexible ideas for the SAC. Although the bad thing was that I froze sometimes because I thought I was expressing myself a bit noobly.
I also got told to edit my conclusions throughout this exam period and try make them as beastly as possible, because that's the last thing examiners read before they assign you your score.