My husband & I just went in January. Our AF son met us on his mid-tour break, and we had a wonderful time.
We actually spent our time on the other island but I would go again even with the 20+ hours of flying. We rented a holiday house, a MIL apt on the back of someone's home, and drove from one side of the country to the other. We drove appox 200 Kilometers in the time we were there. We were in Christchurch, Queensland, the mountains, went whale watching and went to Milford Sound to see the Fjords.
The Kiwis were complaining about the weather, but we enjoyed it since it was 16 deg F here when we left. Wonderful country, people and trip. Congratulations and enjoy yourselves.
Susan