I find that it's best to buy airline tickets early..but not TOO early.
Airlines put out a price apx 300 days in advance of flights. These prices are usually higher than normal. They do this to fish and see who will jump on and lock in the higher prices. Some people insist that the sooner you get the tickets, the safer you are and the better off you are.
Then, after a while, the closer you get to the actual departure date, if all the tickets aren't sold, the airline will sometimes LOWER the prices to a rediculously low rate. BE WARNED though..there are only a FEW of these tickets available at this really low rate. Again, this is to suck in customers.
Then, the closer it gets to departure time, the prices slowly go up again.
At this point, the tickets will get higher and higher the closer the departure date comes.
It's not unusual to have tickets prices go up and down 10 or 12 times before a flight. My advice is to keep checking back to the airline for ticket prices...and when you feel they are at their lowest, buy your tickets. It's a lot of work, but my wife and I have gotten some really good rates by keeping a close eye on Flight prices.
Also: For those of you who don't care what time you arrive and don't use magical express or have a limo waiting in Orlando, sometimes the flights are overbooked and the airlines will offer you as much as $300 to give up your seats on that particular flight. The $300 comes in the form of a travel voucher so if you are willing to sit around at the airport until the next flight to Orlando, you can accumulate big $$$ for your next Disney vacation.
Flying these days, and at the same time trying to get a good rate, is a lot of work...but it pays off if you do a little research before you leave.
Hope this helps.