It really depends on how long the Work Visa is granted for. A second or subsequent South Island Contribution Work Visa will be valid for the length of time required to determine the in-progress South Island Contribution Resident Visa application (
WR7.25(c)); there's therefore no guarantee that it will be for 30 months (JoeyGo's answer above is wrong).
If you are approved a Work Visa for 24 months or longer, then
E3.10(b) will be applied: you may be granted the full duration of the visa regardless of the passport's expiration date, and if the visa is granted beyond the expiration of the passport, you will be informed in writing that you will need to transfer the visa into your new passport in order to travel in and out of New Zealand on that passport.
If you are not approved a Work Visa for 24 months or longer, then
E3.11 may into play if there's an imminent passport expiration. If the visa would have been granted beyond the expiration of the passport, INZ will instead only grant the visa up until the expiry date of the passport, and inform you in writing of the day the visa would have expired had the passport remained valid. Once you receive your new passport, you will then transfer your visa to your new passport, and INZ will then vary the visa so that the expiry date matches the intended currency of the visa as specified when it was originally granted.
In short: if you are able to obtain a new passport in good time before the previous one expires, there's little to worry about
: just remember to transfer the visa to the new passport when you obtain it.
The above instructions apply for
all temporary entry class visas. For residence class visas,
R7 applies instead (so you may want to look at that too, in case the South Island Contribution Resident Visa is granted before the original passport expires).