Traditional Economic Lot Size (ELS) calculations determine the optimal lot size to balance the costs of holding inventory with the costs of setting up or changing over production lines (see How Much is Enough without being Too Much).  One significant shortfall of ELS is that it assumes demand is constant and the cost of inventory is directly proportional to the number of units produced.  However, that is rarely true in practice.

Many consumer items (such as food) have a fixed shelf life and variable demand. In this situation, obsolescence costs are not directly proportional to production lot size.  At lower lot sizes, the risk of obsolescence may be negligible.  As lot size increases beyond a certain point, expected obsolescence costs increase faster.  With a little more math, ELS can be adapted for this situation.