An item, whose length of life T is a random variable with cdf F(t) and mean µ, is placed in service at time t = 0. At times {xk} , k =1, 2,..., the item is checked to see if whether or not it is still in a good state (x0 = 0 ). If the item is found to be in a good state, it is continued in service. This is kept up until one of the checks reveals that the item has failed.