Important: Bearing type and temperature matter
The life and reliability of all DC fans, regardless of manufacturer, depends on a combination of voltage, frequency, ambient temperature, and airflow restrictions. The normal failure mode is in the bearing system, which is usually related to the total temperature that the bearings are subjected to, although other factors may apply.
In general, there is not much difference in life between sleeve and ball bearings when the total temperature is relatively low. As this total temperature increases, however, ball bearings will give a progressively longer life than sleeve bearings.