I think the benefits of weight reduction in a pack vs. longevity are minimal. Therefore I would be inclined to overpack at the onset of the Long Walk, were I to indulge in it.
Some packables-
Food-
beans, raisons, candy, jerky.
Electronics-
Cell, mp3 w/audiobooks.
Optional-
Glock 36 (hey, you never know, at the conclusion of my Walk, I'm not going down easy, or alone))
duct tape (shoe repair)
socks
Although I am completely sober at all times, I'd be inclined to bring some strong pain reducing drugs. I mean effective.
Discuss.