In the 4 summers we have been going to Orlando (this will be our 5th), I have never bought airline tickets more than 4 months in advance. Too many things can happen, like another Fairytale Package might come out and then we'll want to extend our stay, but can't unless we pay a fee to change the airline tickets. Things like that.
Also, as far as prices go, I have never paid over $200 for tix from NYC to MCO. In fact, last year, the prices were consistently around $200 for the 4th of July week, but I held out, because I knew they price would come down. And it sure did. I paid $175 for myself, and my 2 sons, and $155 for DH who joined us a day later. We got prime seats in row 2 on Song, and we were very happy.
I watch the fares daily just to see what's going on, and I always check to see how booked the seats are. Around March, I'll be watching for the web specials, which sometimes only last for a few hours, and keep my fingers crossed for a repeat of last year. I am so confident it will continue to be the same way as it's been!