Moving from a partner-sponsored work visa to partner-sponsored residence is based on the fact of a proven partnership - consistently living with the partner who is a NZ citizen or resident. If an applicant doesn't apply for another partnership based visa when the first one is coming up for expiry, INZ tend to suspect that the partnership has broken down, so it isn't as straightforward to move onto a further partner-sponsored visa later.
Also, you would not normally be eligible for a WHV in your situation - already set up living in NZ with a job and a partner. It's a working HOLIDAY visa. It's for people who have a life set up in another country that they're going to go back to after their sight-seeing visit to New Zealand.