If you spent most of the next two years in your original home country, then came back to NZ just before expiry of your travel conditions, that would be fine, as long as you were coming back to settle and make your life there at that point - you would not be able to renew your travel conditions (to be able to travel outside the country) for very long at that time if you could hardly show any time in NZ to date. You would need to be prepared to settle down and establish your commitment to NZ, counting from then on. (In other words, you would probably, using the most common criterion for commitment, need to accept that you would not be able to travel outside NZ for the following two years, so as to get the right to Permanent Residence, then after that you would be able to come and go freely.)