I think it depends. Usually, prices are a little higher if it's too early. I have been watching prices for our July trip since January. I finally got a good rate of $176.90 round trip (incl. fees and taxes) through SouthWest from PHL to MCO, but that was on the day they released the new dates thru August (I think it was February 17th). I would just say be diligent in checking and rechecking, and if you see a price that looks good to you, grab it. I missed a deal of $159 through Spirit Air out of Atlantic City. I was beginning to think I wouldn't get anything under $200, but I waited for SouthWest and was lucky. Now, I was just trying to help a friend who's planning on going the end of June, and I couldn't find anything for her in our area for under $259 (this is for non-stop flights), and USAir wanted $512 per person round trip! I don't know if the anticipated gas price increases are affecting airfaire or what, but the rates seem pretty high to me right now. Good luck to you. Hopefully others will have some tips for you as well.
Sheri