The optimal production run time is more sensitive to the setup cost,
while the optimal preventive maintenance frequency is more sensitive to the preventive maintenance cost.
For further research, this paper can be extended to consider the situation with non-instantaneous repair. This
paper considers instantaneous repair to simplify the mode. It is valuable to determine the production and maintenance
decisions when repair is not instantaneous. For deteriorating items such as medicine, volatile liquids, foodstuffs, etc.,
product quantity decreases due to deterioration during their normal storage period. One may incorporate the
characteristics of deteriorating items into our model for further research. When customer demand exceeds
manufacturer supply, a shortage occurs. Considering shortage allowance is also another interesting research topic.