AlexanderB,
My assessment day started at 0830 and finished at 1700. They say aviation is hours of boredom punctuated by moments of sheer terror, but I think they were actually talking about the recruitment process
Jokes aside, thats how long mine took (eight and a half hours!). I was also asked Navy and Army questions even though RAAF was my first preference. These were things like, "what is the new Navy/Army helicopter?" and "Where and how long is initial training for Army?" and so on. Not all interviewers are the same, some won't ask much more than "what is the aircraft on that poster on the wall?" but I've heard others will really dig deep. Spare no effort and you'll give yourself every chance of success.