We're going in May. Already have our hotel and passes but still waiting for airline tickets. I just keep checking and if the price is really good, I book at that time. If not, I keep checking. I've booked as far away as 6 months to as close as one month and have always gotten good rates. We've been flying to Disney for about 10 years now and I've never not found good rates.
Our highest rates were $150 per person and our lowest were $120 per person. We've flown Continental, US Air, United, Southwest and Air Tran. Our last time was January with Continental for $120 round trip per person. I guess it all depends on how nervous you get. If it really bothers you to wait, and you find a rate you can live with, go for it. Personally, I prefer to wait and I've never been disappointed. But that's just me.
It also depends on where you fly out of. We used to live in Vermont and the closest airport was Burlington International, which has very high rates. We ended up flying out of Manchester, NH when we went to California and saved about $600 for both of us. We're flying to California in March and got our tickets out of Columbus for $171.00 per person round trip. Here in Ohio, we have our choice of airports so that makes a big difference in price. We can pick and choose so we have a better opportunity of getting a good rate. You have to do what's comfortable for you. Good luck. I hope you get a good rate.