Second and third quarters are traditionally the busiest and most profitable for commercial carriers, thus, the cheapest buckets are either being highly restricted or are selling out early. Fuel costs are also insane right now and carriers are doing their best to increase fares with fuel surcharges where possible. If you are looking to maximize miles and minimize costs, in my experience, it's easiest in the first and fourth quarters.

If you're bent on traveling between May and October, I'd suggest waiting it out for a bit as a lot of people are booking summer vacations right now. Just because there aren't any cheap seats now doesn't mean there won't be more released into the lower fare buckets later. The deals may be a little harder to find, but they'll come (this hypothetical is totally out the window for trips to Europe this summer!). It also may sound strange, but if you're looking at deals, try AA for AS miles; there are more AS flight numbers on AA metal right now than I've ever seen before. While you may have to fly more miles to make MVP or MVPG by flying partners, the total qualifying cost can still be kept much lower than if you simply flew AS alone.

I'm interested in going SEA-TUS-SEA in late July; right now the best fares are about $305-$425, with less than 10 seats sold on each flight. I'm willing to gamble that this will drop to about $225-250 in the next month or so, as TUS isn't exactly at the height of tourist popularity in the middle of summer. I'll book the hotel and rental car now (real cheap!) and wait it out on the airfare.