I see the logic but cannot imagine taking a MRE's for any long journey. Too heavy and too hard to palate on a day-to-day basis.

I would imagine water would be the most difficult item to procure on a 400 mile, foot journey. Maybe in the Pacific NW or comparable area. In most areas it would be tough.
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No, I am not Bear Grylls, but I stayed at a Holiday Inn Express last night and Bear was there too!