This Reagent Pack is for use with Taylor Colorimeters. All reagents have a shelf life, whether they are liquids, powders, crystals, tablets, or test-strip pads. If kept dry, powders and crystals are very stable. Acids are also long lived. Date of manufacture is not the controlling factor when it comes to shelf life. Storage conditions are more important. As with all perishables, reagents are sensitive to environmental influences and will last longer under controlled conditions.