Australian Reentry

Hi, currently in Macau and leave tomorrow, my 'visa free entry' expires next week (been here for 3 week already).
I am about to go home to Australia and return in 2 weeks, for an additional 20 days. I was wondering if any "grace period" is needed to get another 30 days or if my 30 days is replenished once I get back home?
I'm getting mixed responses from associates that I need I to be home for 72 hours and another that I need to be home for 30 days prior to reentry.