I booked our August flights from Buffalo on JetBlue in December 2013 as soon as I saw them come out. I've checked back regularly and I've never seen them lower than what I paid. It's been close a few times (paid about $400), and it's been over double a lot of the time, even seen triple. I liked the flights we booked because they are early morning (8AM) and direct non-stop on the way there, and later afternoon (6PM) non-stop on the way home. Gives us more time in The World.
I have seen a lot more variation on price for flights out of Pearson, especially if you don't mind later flights and one or more stops. There have been times it would have been cheaper to fly out of Toronto, but it'd have meant leaving later in the afternoon, and flying home early in the morning with multiple stops.