they last the life of the Airframe ?
That is the dream of all maintenance staff...
No. They do not last very long, on some reginal jets you may have to replace them as frequent as every 2 years. They consist of several bonded layers of glass and/or trasparent plastics, as they are subjected to UV and huge temperature changes, the adhesive ages and you get delaminations. The seals do also age and you get water ingress (no good idea if you freeze it or have an electric heating as part of thze design...). Additionally they sometimes crack, if they are installed with build in stress due to typical tolerances not accounted for in the design.
Industry is still waiting for a company which designs long lasting cockpit windows.