What is the main advantage that managers will gain by using a perpetual inventory system?. At any point in time, managers know their inventory turnover rates. b. At any point in time, manogers know how much product should be in inventory. At the end of the year, storage-related product costs will be lower for managers using the perpetual inventory system. At the end of she year, storage-related lobor costs will be lower for managers using the perpetual inventory system