Sorry, but you've really got to plan ahead for these sorts of things, and not just on Delta. All airlines are pretty much like that. I managed to snag some award seats on DL/AF/AZ for this May, but I booked them in February/March, and managed to slip in under the AF cutoff as well. I would suggest traveling in the fall when you'd have a much better chance of finding those tickets, or else go ahead and book now for next summer.