I am seriously considering running the Back2Back Challenge marathons next January, as in back to back days! That would be the Mississippi Blues Marathon (Jackson, MS) on Saturday and the First Light Marathon (Mobile, AL) on Sunday. These events are separated by several hours driving time, too. I think this would be more of an interest and challenge to me than going after another marathon PR. I only need to knock off about 5 minutes to qualify for Boston under the new rules, but there would be no chance to knock off the extra 20 minutes it would take to get an opportunity to actually run it. So, the Boston lure is no longer there. Now, back to the challenge at hand.
We all know how sore you can be after a marathon. Now take that marathon soreness right into the next morning and run another marathon. Hmmm. My goal would be to run both events at nearly the same pace, although I have no idea what that might be yet. It wouldn't bother me a bit to run each marathon 45 minutes slower than my last marathon time. Maybe even an hour slower. Not sure I would like the thought of making them any longer. 
I believe I will train for these events as I normally would a marathon. The only difference I plan for sure is a few weekend back to back runs during the peak of training. Maybe a 20 miler on a Saturday followed by a 10 miler on Sunday. During those sessions, I would hope to dial in a two-marathon pace.
So, there is the plan...for the moment. I reserve the right to bail out without a single disappointment over it. This is all just a different sort of challenge for me. The primary purpose is to keep the running goals interesting each year and keep the fun in running. Let's go have fun!