An inventory management method is also provided. This method includes removing and replacing the gas product from a first salt cavern as supply and demand dictate, analyzing the impurities in the gas product that is removed, predicting the duration until a maximum acceptable impurity limit is present, removing all the working gas from the first salt cavern when the maximum acceptable impurity limit is reached, then replacing the working gas in the first salt cavern, while concurrently, removing and replacing the gas product from a second salt cavern as supply and demand dictate, analyzing the impurities in the gas product that is removed, predicting the duration until a maximum acceptable impurity limit is present, removing all the working gas from the second salt cavern when the maximum acceptable impurity limit is reached, then replacing the working gas in the second salt cavern, while concurrently repeating steps a)-g).