In addition to the parent residence categories, parents of NZ residents or citizens are permitted to remain for a maximum of 18 months within a three-year timeframe on a multiple-entry parent/grandparent visitor visa.
The Government has been working on, and is due to release, a new 5-year "Parent Boost" visa next year.
The new visa may require the ability to cover possible healthcare expenses and to this effect the Government is also considering a healthcare levy. The levy system is in place in several other countries. Some NZ visa categories include the requirement to hold a comprehensive insurance to ensure the NZ taxpayer doesn't have to foot the bill if the person falls sick, and this may be a requirement too.
Like all visa applications intending a stay of 12 months or more, it will be a requirement to demonstrate an "acceptable standard of health" by immigration's definition. It is important to discuss any concerns you may have with a licensed immigration adviser before an application is submitted. This allows to mitigate concerns, or discuss a strategy to speed up visa processing, or minimise the risk of decline.
The goal is to implement this visa by 30 November 2025.