though most studies on periodic-review inventory models have (implicitly) assumed that the review periods are as small as one day (see, e.g., [5] and references therein), periodic-review systems in practice often have the review periods (i.e., replenishment cycles or simply cycles) that are a few days or weeks long and regular orders are placed at a review epoch (see, e.g., [2] and [3] for periodic systems where an emergency order can be placed at a review epoch or virtually at any time between two review epochs).