Immigration New Zealand is very strict and for reminder, please have a confirmed and extensive itinerary, hotels and others booking before you reached New Zealand. Please print all of your itinerary and booking evidence and put it in one file and back up of soft copy.
From our experience, after we have passed the immigration inspection for passport stamping, we have been stopped by the immigration for 3 times just within the airport area and have been asked on the same question which is about our activity and planning in New Zealand. Luckily, we manage to tell them one by one for 14 days of our itinerary and our explanation was convincing.
If you don’t have any firm itinerary, I think you will spend more time at the airport with the immigration.
Having mentioned that, we understood the practice as part of Immigration New Zealand’s role is to make sure people coming to New Zealand do not pose any potential risk to the country.
You may refer more about immigration at link below: