Question: What is the shelf life of your products after they are opened, or not opened? Thanks, Dale. Answer: Dale, the products have excellent shelf life, but there is some variation from product to product. 1. OPTIMIZE will last the rest of our lives opened or unopened. 2. MAXIMIZE is equally durable and viable and will store indefinitely. 3. PENETRATE keeps a long time, but after one year, we noticed that the bacterial counts in Part B begin to decline slightly, so you get the most active product if you use it within one year, and of course, you need to keep 'A' and 'B' in separate containers. Once you mix them, there is virtually no shelf life and it should be used within 12 hours. 4. NOURISH-Biosol keeps for several years in an unopened bag (should be used within 5 years). Once you open it, you need to seal it well for storage and keep as dry as possible. If an open bag is not resealed and the NOURISH is exposed to moisture in the air, usually a mold will begin to grow on it and while it will still be useable, that is the first step to decreased viability. The three dry products, OPTIMIZE, MAXIMIZE and NOURISH can be mixed together and applied all at once for convenience, but they will not store for more than a few days in this mixed state. If you mix them together you need to apply them immediately. Thank you for your interest! John