In industry, it is common to prioritize some orders over others. This is done to reduce the lead time and waiting time of these prioritized orders, hence the customer will get the order earlier than otherwise. However, whenever an order is prioritized, the remaining orders are de-prioritized, and their lead time and waiting time will increase. In industry, a rule of the thumb that no more than 30% of the orders should be prioritized is often used. This paper will verify this assumption using simulations for different conditions. It will show that this rule of thumb is generally a valid approach. The paper will offer more detail on the trade-off between prioritizing some orders and hence delaying other orders.