Any examples that are out-dated or that 'have been'/'are being' used by many people should be avoided, unless you can add something unique and relevant to them. Textbooks will often have generic examples which are boring and people will have used those in essays a lot. As for examples in the examiner's report, many of them could be outdated by now, and other people will also have read the examiner's reports, so I would be wary of those. Two topics people will be talking about alot are Ruddspeak and the bushfires - these are relevant examples, which is good, but they will be used by many people, so you must ensure that your exposition and analysis is unique, perhaps including a few interesting quotes or commentary by linguists such as Don Watson.
You can't really pre-prepare essays since you can be sure the examiners will not repeat a question they have asked previously, and if the pre-prepared essay does not capture the essence of the question, it will look off-topic or irrelevant. The stimulus material will also need to be worked into your essay, and in fact it can serve as a guide when you write your paragraphs, since the stimulus material can often encapsulate several facets of an essay question.
Having said that, if a pre-prepared example or even paragraph fits perfectly into the essay question, by all means, regurgitate.