I knew about the Part C volatility from a posting by Photo Engineer a while back, so it is to be expected with open concentrates. But sealed, the shelf life should be at least the 2 - 3 years indicated by Sebastian. Freestyle gave me a credit for the one remaining kit that I can no longer use, and I decided to apply it toward a Maxi kit since I will need it when I return from vacation next month. According to the rep I spoke with, the issue was only with the Midi kits, and they have sent their remaining stock back to the manufacturer.