Just in case you haven't heard of this, thought I'd mention the Longest Day Ride. It's a virtual event in which riders all over New Zealand ride all day long on the longest day of the year. People link up and share their plans/experiences on the website linked above, and it's a bit of a fundraiser for Arthritis NZ. If you're looking for an excuse to get in one really long ride before Christmas, this is a good one. Doesn't matter where you are, just work out a really epic ride in your part of the country and go for it.
I suggest you follow that up with at least one overnight bike trip over the Christmas holidays. If you can test your gear and have some fun, you'll be that much more relaxed coming into the Brevet or Brevette. And if something doesn't quite work, you'll still have time to test something different.
There have been a couple of enquiries about what a cruisy Brevette schedule might look like. It depends a bit on your particular riding strengths and weaknesses, and if you will be camping for booking cabins/motel rooms. Here's a rough plan that is fairly easy on the legs and has a spare half day at the end:
Sat - Blenheim to Picton (approx 70k)
Sun - Picton to Nelson (approx 85k)
Mon - Nelson to St Arnaud (87k)
Tues - St Arnaud to Murchison (approx 70k)
Wed - Murchison to Springs Junction (approx 80k)
Thurs - Springs Junction to Hanmer (92k)
Fri - Hanmer to St Arnaud (112k, or 105k if camping near Tophouse)
Sat - St Arnaud to Blenheim (approx 110k, or 103'ish if camping near Tophouse)
Sun - Spare