I think with the AirTran integration, they will be slowing up on releases. The next release will only be 1 month.
I agree that release dates are likely to more unpredictable as they deal with the AirTran integration, but one-month releases aren't necessarily that unusual. See below for 2010's weird releases as an example. On Sept. 28 they opened a month and a half of dates, then just nine days later they opened another five weeks of dates.
2010
03/23/2010 opened through 11/05/2010
06/15/2010 opened through 01/07/2011
08/17/2010 opened through 03/11/2011
09/28/2010 opened through 04/25/2011
10/07/2010 opened through 06/03/2011
11/16/2010 opened through 08/12/2011
Speculation at the time was they wanted to book additional revenue in their 3Q earnings, so they gave themselves three days of sales (Sept. 28-30) to do that. Bottom line is lots of factors can dictate when they open up dates.
You can see a full list of the last few year's openings
here.