Yep, what Richard said. Book using the onboard booking discount first to ensure yourself some amount of savings. Typically Disney only discounts cruises that aren't selling well. If a discount is released for a cruise it oftentimes happens closer to the time of sailing. For instance, the Fantasy cruise I'm booked on for 9/14/13 released a general public guaranteed rate less than 60 days prior to sailing. In the past day or so a DVC members rate came out, too. It's whatever will get the ship numbers up. There's no set pattern as to which sailings will get discounted and what discounts will become available. If you're traveling during an "off" season then your chances would be better. But, there's no telling for sure if a military rate will release, when it will happen, or what type of discount will roll out. If you initially go with the OBB deal you're at least guaranteed to have those savings and onboard credits to spend.
