Maybe one seat per year if your lucky.

If you want to fly up front on NZ, and not using NZ points you pretty will have to pay for.

Note that NZ's A320s are all Y, which operate most Tasman flights apart from an couple of 777/789/767 services ex-AKL.

On the Tasman NZ sells its PE product on the 77W,772,789 for about $400NZD oneway could be an better option if you didn't want to pay for J.