Why renew?
I'm not an authority so you will need to get confirmation, but my understanding is as follows:
If you are not planning to fly in NZ at the moment you don't need to do a BFR as your PPL is a lifetime licence. When you come back here and want to fly, do the BFR then.
A word of warning though - the 'lifetime' statement is bull****. If you do nothing for 5 years (no flying, no medical etc) you will need to do the flight test again. A mate of mine with an NZ CPL came back from SA as he had a job with a regional. Had to do his CPL flight test and Law exam again (effectively he had to convert his SA licence to an NZ one) as it was 5 years and 10 weeks since he had done anything here. I believe if he had simpy renewed his medical once during that time he would have been alright. Check it out with the CAA.