On the morning of August 5, 180 days before our check in date of Feb 1 2007, I woke up at 6:45 am EST and started dialing. I got through right away and was dismayed to find out that CRT was completely booked on the day I wanted (Feb 3, the second morning of our stay.) I WAS able to get a reservation for the LAST morning of our stay. This makes sense because for 7 days prior to my calling, that second morning had been available to Disney Resort guests making 180 +10 ADR's. So people had already been booking CRT since July 29. The last morning of our stay had only been made available to Disney guests since August 3, two days prior to my calling. Hence, CRT was not completely booked for the later date.
So my advice: when doing your planning, try to schedule the more popular, hard to get restaurants for the latter days of your trip. You will be more likely to get the date and time you want.