Legislation ATT/CTA

I have couple of questions regarding use of legislation in exams. Firstly how vital is legislation in ATT exam? I have been told that for ATT exams you can do without legislation however for CTA exams one must be able to use legislation effectively in exams. So is it worth starting to get familiar with legislation while doing ATT exams in anticipation of future CTA exams?

Secondly if I buy legislation for Nov'12 exams do I need to buy another set for May'13 exams?

I will be very grateful for your help and any recommendations

Many thanks