This graph shows the election dates for every election since WWII. Basically up until 2014 every election was in November except for the three snap elections (and the elections just after them, as they must be held within around 38 months of the last one).
It was only in 2014 that it was held early, and that was to avoid the G20 meeting NZ had been invited to.
So if the election is delayed until November, that is not a big issue. November is the traditional month anyway.