I am traveling from DFW to AKL, on a one-way flight and will arrive at 8:45am:

I am trying to get to a different city in New Zealand (such as Christchurch or Wellington, to be decided) on the same day in New Zealand. However these would be on separate tickets using Air New Zealand. Largely due to this site, I am aware that separate tickets come with an extra risk, which is why it probably makes sense to give me a lot of layover time. Furthermore, I am also going to have checked luggage.

However the good news is that Air New Zealand has a lot of options from Auckland to other major cities, with flights leaving almost every hour. If you were a US citizen flying at this time, and not bringing in any complex supplies (e.g., agriculture) that immigration officials might need to inspect, I am wondering:

• How much of a layover time would you be comfortable with in Auckland, before the next domestic (within New Zealand) flight on a separate ticket? 6 hours? 8 hours? I am thinking of going with 8 hours.
• What would you do as part of this research for your booking? For example, I was hoping to see the on-time flight statistics from DFW to AKL but it seems like this is a new flight route so there is no performance history (but I could check this when the date gets closer). Another option could be to check and see how many international flights arrive in Auckland that time, and judge the layover time accordingly?

I am aware that there are many factors that come into play, so I'm just hoping to see what your immediate thoughts might be.