What's the punctuality rate? Is two and a half hours transfer time enough ?

Here's my experience with a layover. I had a two-hour layover in Auckland before my flight to Christchurch. Both were Air New Zealand flights. They said that once your luggage goes through customs, you can just hand it over to the transfer luggage counter. But if your flight is taking off in an hour or so, you still need to bring your luggage to the domestic counter to check it in. Of course, this is the most secure way, otherwise it's hard to say whether your luggage will make it to your destination on time. Second, our flight was delayed by 20 minutes that day, and only three counters were open for customs clearance, which was very slow and stressful. Third, whether you declare or don't declare, the queue is very long. We were already one of the earlier passengers to come out of the first cabin, and then we ran to the customs clearance line, ran through the declaration, and only after running to the domestic terminal did we just make it on time.