As noted, L10 life is defined by the life of the bearings. To better understand this, the customer can look at the service life of a cooling fan in reference to the bearing degradation over the product life. Internal to every bearing is an inner race, outer race, and lubrication grease. As a fan operates, the internal grease will begin to degrade as it is worn down over time. As the grease degrades, it will begin to become more viscous and allow for higher friction within the bearing. This will directly cause a decrease in the fan speed as the product moves towards end of life. Once a fan drops below 70% of the rated speed, the customer can consider the fan has reached the end of it’s operating life.