In my military life I can relate the reason for the expiration date on the bag is due to the bag not the fluid. Plastic is not impermeable. The rationale is after the date of expiration enough time has passed to question the integrity of the fluid. The purity of the fluid can be compromised. If you started a line and pushed the fluid you have a increased risk of infection. The fluid is perfectly good for oral use. It doesn't taste very good but in a pinch it works. - Ken L.