It is easy to justify frequent condition monitoring for high criticality machines, even when high reliability is being achieved. When high reliability is achieved for medium and lower criticality machines, it becomes harder to justify frequent monitoring. It is not uncommon for managers without a good understanding of condition monitoring to want to eliminate condition monitoring costs from their budgets, so you need a way to justify the amount of monitoring you are carrying out. This presentation will give a method for finding the optimum condition monitoring frequencies to minimise overall business costs. If you do decide to monitor less often then there is an increased risk that a failure will sneak through undetected. A method is given to protect condition monitoring personnel from blame for failures due to monitoring frequencies being reduced to minimise overall business costs.