A remarkable deal of recent research in process management is devoted to combining the maintenance policies with statistical process control models such as optimal design of control charts. To optimize the design parameters (the sample size, the sampling intervals, the control limits coefficient, the maintenance level and the truncated time), Rahim and Banerjee and Ben-Daya and Rahim generalized cost models simplified the joint models of maintenance and economic design of control charts by assuming constant integrated hazard over sampling intervals. As an alternative to the constant approach, a decreasing integrated hazard procedure is applied in this paper for determining the inspection intervals as a conservative strategy along with increase in overall cost. A numerical study based on the -control chart with normal quality characteristic distribution and Weibull () shock model is provided to investigate the performance of this approach in comparison with the traditional one.