Car warranty claim rejection

After my car was paid off, I decided to take out a mechanical warrantee through dotsure. My car has full franchise service history, so the car has been properly mainted and serviced. My timing chain kit recently failed, and this is covered under the schedule of parts on dotsure's warrantee policy documents, however my claim was denied because they say this is due to normal wear and tear. At first they said that this should have been replaced during servicing at Renault, however I confirmed with Renault that the timing chain kit is a lifetime item and only needs to be replaced when it becomes noisy. I could understand if the claim was denied if the car had not been maintained and serviced properly, however this was not the case. I feel they will use the 'wear and tear' card whereever possible. I would stay away.