Not to discount that method Ironraven, but that also leaves your kit without the main MRE shell. The broken down / stripped down versions are meant to be consumed soon or when your pack simply doesn't have the space for a mission. But once you break the outer seal on the overall pack, you lose some containment/protection. I'm not saying that the entree or other items are going to break down immediately or anything, but I'd be willing to bet money that they break down faster than the MREs which are left intact.

So I think that tactic depends on your goals. If it's long term storage for emergencies, keep them cool and intact. If you are going camping with them or know they'll be rotated out in a year or less, it's probably not an issue. I'm just throwing out a number on that... I have no earthly idea what the degradation is without it's outer shell. If nothing else, I know that the internal packs would develop fewer failures due to rough handling. Maybe one could vacuum seal custom packs after buying the parts? Probably not quite as good, but would certainly offer benefits.