Automotive Plastics: Third brakelight plastice, degradation on ABS plastics

Question
Octavio,
A mechanic trying to lower the rear sunshade(the result of a faulty motor) on my car cracked the plastic frame surrounding my third brake light. He refuses to replace the cracked housing saying that because the car is ten years old the plastic was damaged by age and sun and consequently not his fault.Realistically what's the useable life span for this type of part? The car has less 100K miles on it and is garage kept.
Thanks,
Scott

Answer
Hi Scott, Your mechanic may be right. If this part was subject to photo-degradation, it is easy to verify: with bare hands, try to twist any apparently sound tab, appendage or area with the force a normal piece would resist. Depending on the result of this test you can proceed...
thanks for asking.