> All in one systems with water heating are way too complex and _will_ fail relatively quickly, ...

Can you offer some evidence of this? I don't see how adding a refrigerant to water heat exchanger after the compressor, before the reversing valve, could possibly hurt the longevity of a system.

> ... mini heat pumps won't last 10 years, and by the time it dies you won't be able to find a replacement for your specific model

Thing with mini-splits is you replace the entire unit so it doesn't matter.

This makes me sad. I’m in a 1940s house where the lack of it being airtight is a key reason it’s still standing as it leaks and the airflow dries it. Water flows down the inside of the brickwork, and the cavity is well ventilated.

Yay for New Zealand housing.