Hiya,
I'm applying for the prospective marriage visa which is different as you don't have to be living together. I've done quite a lot of reading on this category of migration to Oz and the Australian Immigration website is really helpful. I think for the De Facto visa they are quite strict about the 12 months.The link is
Australian Immigration Fact Sheet 35. One-Year Relationship Requirement so you might be able to find some answers there. If not I have called the Australia High Commisson in UK a couple of times and they were really helpful.
Sorry I couldn't answer any more specifically but I hope that helps a bit!
Nina