Length & Pace of Visit
This really depends on each individual. There are some people who like to move very fast and see the whole country in 10 days (just about possible with your own helicopter). And there are others who like to spend a week just on one small region. We rely on our clients to guide us as to what sort of experience they are after. Most people say that the trip here is a “once in a lifetime” and that therefore they want to see as much as possible just this once. Then they come back again!
We would recommend 2+ weeks to do a country-wide tour, and any time under that prioritised in certain regions. Many tourists over here complain about the pace set by their travel agents (too fast) and how it takes longer to get from point to point in New Zealand as the roads are narrower and windier. We have yet to hear from anyone who thinks they have spent too long in any particular region!
So the answer is - stay as long as you can and don't accept too rushed an itinerary. We can keep anyone busy here for a good two months, and some people never leave. If you have less time, limit the distances you need to travel so as to fully enjoy what you do see.