It does say SPECIFICALLY on the immigration website that you need to have lived together for 12 months, and even if you're 1 week short you need to wait to apply until you've lived together for 12 months. BUT, I've heard of quite a few cases where people went ahead and applied anyway and it hasn't mattered at all. I think it really depends on WHY you're applying when you're 2 weeks short, and a bunch of other factors about your relationship.
Like if you're 2 weeks short of the living together requirement, but you've been in a relationship for several years, it's probably not going to matter, since you can easily claim that you were essentially in a defacto relationship even prior to officially moving in. However if you're 2 weeks short of the 12 months living arrangement, AND you moved in together after dating for just a few months, it's going to seem as if you moved in together to facilitate immigration or a visa of some sort. They might question that more.
Basically, if your relationship is totally legit, you've been together for a long time, you intend to be together forever, etc... probably 2 weeks is going to be irrelevant to immigration. BUT, no matter what your situation is, you do run the risk of being denied, because ultimately they do have grounds to deny you and someone in immigration could be having a bad day and feel like being a d!ck. Obviously, you didn't elaborate too much on your particular situation so it's hard to tell if immigration will judge that you could have waited to apply, or if you could wait. I'd say if you can wait 2 weeks, do. You don't want to give them any reason to deny you.
Also, I think it's more likely that you'll be denied for this if you're applying from within
Australia, because it could look like you came here, needed a way to stay, and the relationship exists to facilitate your (or your partners, not clear on who's applying here) ability to stay in the country.
Might be able to give you a better idea of your chances if you gave a few more details of your situation?