Could still be worth a Seatspy alert just in case J, or even F availability appears. It does happen!

We got return J tickets to Sydney last year in Feb for travel in April. I think there must have been some kind of mass release of Avios seats as we could have chosen from a number of dates in April. In the end we changed both legs as 2 F tickets appeared about 6 weeks before we flew which we snapped up, and we changed the return leg to fly back with Qatar, again Avios availability appeared and we thought we would prefer Qatar. We also used Avios to fly from Sydney to Wellington, and paid for the return leg from Queenstown to Sydney.

if your flights to and from NZ are on a seperate ticket give yourself plenty of contingency time. Our flight from Queenstown to Sydney was cancelled while we were in the Queenstown lounge due to bad weather and we couldn’t get another flight for about 36 hours. Our daughter and son in law who were with us missed their flight home from Sydney and had to pay for new tickets home!