We booked for November at the beginning of March....I don't think this was the earliest I could have booked but I waited for the 40% off offer. A lot of people are hoping Disney will stick to their patterns and release a similar offer next March
If you don't already know, the xmas stuff in DLP starts on the second week of november. If you went a week later, you would get more for your money in terms of shows and atmosphere (hopefully! I'm going in 10 days so watch out for my trip report when I get back!)