I’ve noticed there were quite a few short notice NZ sales in the last 12 months. Like the Hawaii price war at the moment. There’s always been short notice specials for mid Nov-mid Dec travel to the US I’ve noticed.

Also lately the airlines seemed to be offering really cheap specials via the travel agent shops like flight centre and house of travel. The flight centre expo in Late September in Wellington has some of the cheapest deals. I find sky scanner useful sometimes but there’s really not much competition for NZ on the Nz US routes unless you’re prepared to fly via OZ. Sorry this doesn’t answer your question specifically!!