That said, it probably is not necessary to point out that I am no guru when it comes to what YOU should eat on your long runs. I'm just an expert on what seems to work for me. I say "seems" to work for me because I think it's mostly mental.
I started mulling this whole thing over after finishing last weekend's Austin Marathon. I had lots of time to mull before and between flights home at AUS and LAX.
I determined that when it comes to my training regimen, and the culmination thereof on marathon Sundays, I seek to be more of an artist than a scientist. I am a devouted follower of the Jeff Galloway method, but will admit that there are way too many numbers to digest in the books explaining his plan. I mostly know I'm supposed to run a bit and walk a bit and that the resting bits are as important as the non-resting bits. I think I like the resting bits almost as much as I enjoy the finishing bit. Honestly, I don't overly relish the in-betweens.
What's pulled me through most of the 23 marathons I've done to date (number 24 is just over a week away!) is knowing that I get to honor myself at mile 17 with the candy of my youth in England. Today's Mars bars are just as good as my yesterday's. At some maybe-goofy level having a Mars bridges the gap between the life I wish I'd had in my homeland with the awesome, although decidedly different, life I do have here.
On the science side, I keep track of my miles, my heart rate, the inclines, the declines, and how many miles I have on the current pair of "trainers". I also am a big proponent of the the carbo load, Clif Shots, Accelerade (Mountain Blueberry), the taper, proper hydration, and technical running gear, including proper Garmin 305 operation.
When it comes right down to it, the science part enables the art. But, if I had to choose, I would not do this marathon thing without the latter.
To that end, for you, I would only encourage you to find some way, some place, some time on your own marathon adventure, that you get to honor, acknowledge, to celebrate your self-ness. Even if no one else ever knows.