Hi jessi,
I went to the last Sydney one and one of the girls did the same thing as you except she came from Melbourne and had to change her flight like 3 times! They start at 9am on the Sat, but ours was quite busy so they had two information sessions. This meant that the day went for a bit longer (because we had to wait till both info sessions were over before we did the 2 mins with recruiters), I was home by about 2.30 and I live very close. On the Sunday they do the group interviews which start at 9am but don't have an end time, its just over when its over. I was home by 6.00pm. And then they hold the one on one interviews on the Mon, Tues or Wed. You have a choice of day and time, but if you can't come on the Mon/Tues/Wed then you miss out. They left the country on the Thursday morning. So if you make it all the way through to the one on one, then you would have to stay at least until Monday arvo (best case scenario).
I had to call in sick for work...which I felt bad about but there was just no other choice!
Maybe just get a flight where you don't have to pay for every flight change?