TankTechsRx in a sealed unopened bottle has been tested out to 5 years with no discernable loss of efficacy. An opened bottle has been used for three years with positive results when the last portion was used. TankTechsRx is easy to store but some commonsense precautions will help insure the longevity. Always store it in an airtight closed container to prevent dehydration. Store at as close to room temperature as convenient. Very high temperatures did not affect it in our tests, but best practice is to keep it comfortable. Freezing does not kill the bacteria, but we highly recommend it not be stored where it can be frozen. While it is possible to kill the probiotic bacteria, it is not easy. We deliberately left an open container of TankTechsRx exposed to the elements for several months in Arizona to see how long it would take to kill the bacteria. It made it through the mild Arizona winter just fine but the summer heat finally evaporated enough of the water to finally kill the bacteria. It is very obvious when it is dead. The smell is very offensive. A healthy product will have the smell of fermented molasses. A simple and convenient place to store TankTechsRx in an RV in the off season is in a closed and turned off refrigerator.