Once you understand the failure mode that resulted in the failure and the failure mechanism that resulted in the failure mode, it is possible to begin the process of estimating the usable life of the component. In other words, how quickly is the time bomb ticking toward the failure?

The first thing to ascertain is whether the failure mechanism is present at all times or if it occurs only on a random basis.

For instance, if the pressure sensor diaphragm is intended to flex frequently and continuously, and if the flexure is greater than the fatigue limit of the metal, then deterioration is present all the time. In this situation, the time or number of cycles to failure needs to be monitored, then used as a basis for performing preventive maintenance.

On the other hand, if failures are random, the timing of predictive and preventive maintenance may need to be designed to capture random events. For instance, if the failure is the result of plugging due to random instances when fluid filter maintenance has been forgotten, a form of predictive maintenance capable of capturing events that occur at random times is needed. For example, it might be possible to spot plugging by including an algorithm in control software that identifies instances where the pressure level stops cycling like normal. The buffer provided by partial plugging can be viewed as an explanation for abnormal operation. 

Tip from "Critical Connections: Linking Failure Modes and Failure Mechanisms to Predictive and Preventive Maintenance" by Daniel T. Daley