I do this route all the time (and have been for years), and I think it's unlikely to come down much from the levels you're seeing now if at all. So I guess there's no disadvantage to buying this far in advance. There may, in fact, be an advantage if you can find R inventory, in which case you could possibly upgrade one or both of your flights if you wanted. (it's expensive though, $550 plus 20,000 miles each way to upgrade the lower fares)
And booking early, you'll have a better choice of seats of course (see SeatGuru.com etc)
Oh, non-weekend fares are sometimes slightly lower (maybe $25-$40)
Good luck!