Letter to the Editor—Optimal Replacement Policies for Hyperexponentially and Uniformly Distributed Lifetimes

Policies of block replacement and replacement only of individual failures are compared. Block replacement is never desirable for hyperexponentially distributed lifetimes. For uniformly distributed lifetimes, block replacement is preferred only if the ratio of per item block replacement cost to per item individual replacement cost is less than 0.3863. The optimal time between block replacements is graphed as a function of this ratio.