After a couple of complaints, including from myself I'd like to advise Aussies travelling to Samoa via New Zealand that you cannot buy duty free alcohol in Australia and take it through Auckland International Airport, it will be confiscated. The NZ Customs Officials seem to be the only people aware of this saying someone at the DF section of the airport you depart from should have advised you.
Maybe if you show both boarding passes, ie Aust-NZ-Samoa you'll be told but I wouldn't risk it.
The length of your layover in NZ has no bearing on this, it applies if you have to hang around the transit lounge for hours or if you are going directly from one flight to the next.
Hope this helps some travellers from being ripped offer. Chances are you won't get your money back as the alcohol is no longer in your airport of departure.
Manuia le aso