I have heard of people who risked putting in their application for partner-sponsored Residence just A LITTLE before they have lived together for 12 months, basing this on the idea that by the time a CO has been allocated and is ready to look at their papers, they WILL by then have got 12 months' proof, or if there is a matter of a few days or a week missing by the time the CO is looking, s/he will hold on to things till they qualify. That is the situation that ChrisMWn is thinking of, I believe.
But this would not work for somebody applying 10 months before they qualify. INZ would just reject the application.