Unlike most other exams, IREX is about
what will keep you alive. Confusing altitude v height on an approach
will kill you. And turning up somewhere without enough fuel to wait-out the weather -
that will kill you too. Flying the approach wrong, or out of tolerance ...
that will kill you. Descending below LSA on a dark night surrounded by hills -
now that will kill you! So IREX is much more than just "know the stuff". When you're flying an approach in IMC with no auto-pilot, you'll be busy just doing the right thing - no time to check if it really is the right thing.
Think I'm exaggerating? It's easy enough to find approaches that miss mountains and towers by only a few hundred metres laterally, and a couple of hundred feet vertically. The Canberra VOR and Mudgee NDB come to mind. Get it wrong and we'll see your mess on the news.
IREX is open book - so you should make a note of anything you're uncertain about, and use the time at the end to check uncertain questions against AIP, ERSA etc. (That's what the scrap paper is for, noting things to go back to
) And anyone who walks out of an IREX exam before the time limit, they are just throwing away marks!! Use all the time they give you. Same when you come to your ATPLs.