Google is your friend: USCG Guidelines for Approval of Emergency Provisions for Lifeboats and Liferafts states:

Quote:
Section 5 General requirements for emergency provisions:
d) The emergency provisions should be stable and suitable for storage in the container for a period of five years in temperatures ranging from -30°C to +65°C (-22°F to +149°F).

Actually, it appears that the 5 year shelf life is set at a maximum of five years by the USCG reg. These rations are probably stable and edible even longer, but the regs state that the lifeboat rations must be replaced after five years, so there is no advantage or reason for the companies to claim a longer shelf life.