If anyone has airline pricing figured out I would love to meet them. My best advice is check prices daily and purchase when you feel like your getting a good deal.
I've purchased last minute, literally night before we flew, a few days out, afew weeks and as much as 9 months out. All the years and trips, I've learned that you can't figure out a pattern on pricing and by checking often you can stumble across deals.
I've seen prices high for months then all of a sudden go low for 2 or 3 days then shoot right back up. Basically when I see a good price I grab it and we go, if not then we wait, but I check at least weekly all year long.
Good luck / jamb