10 would probably be ok. Auckland isn't the biggest place in the world. I think we recovered our bags within 30 minutes. Air New Zealand fly the route 20+ times a day (almost every 30 minutes) and you could probably reschedule the flight if necessary.
If you get there early try asking at the info desk if you could be bumped onto an earlier flight. When I was flying from Sydney to Auckland my flight from Townsville got me into Sydney 5 hours early. They were able to put me on an earlier flight that arrived in Auckland nearly 3 hours earlier
