6 months is more than I could hope to get away with, but working on being in the Fiords in March would work for me. As Jon said the main thing for me is to know that there will be other cruising boats around.
As I said at the start of this the fiords are my main interest and after getting a copy of the book Beneath the Reflections produced by Fiordland Marine Guardians my enthusiasm to explore this part of New Zealand has increased to the point where I am sure I can make it happen.