Christchurch branch have a HUGE workload at the moment because of extra applications to cover people working on the reconstruction. We've been hearing of some cases being passed across to other INZ offices in NZ when any of these had some capacity free to help out. Your turn will come. Hang in there.
Also, don't forget that people very often don't hear anything from their CO unless s/he has a query, though s/he will be working on the file meantime. Some people didn't even know they had a CO until s/he contacted them at the very end of the process, for interview (if appropriate) or to tell them they had been approved.