The secondary sealing element (either the O-ring or trapezoid ring) imparts a constant axial force on the metal sealing rings as well as forms a static seal between the housing and the sealing ring. This static seal also drives the shaft torque to the respective sealing ring. The dynamic seal is formed where the two sealing rings meet. Capillary action pulls lubricant up to the point of dynamic sealing and forms a meniscus that seals against debris.
This mechanism of sealing is very durable. Under proper operating conditions, face seals can last for years and often outlast the bearings and other related components.