You said they are covering it so why worry. Fed emissions warranty covers cats for 8 year 80k miles, beyond that it is up the manufacturer or your extended warranty. My fiancee has a Camaro that has failing cats, it got the code at 82k, Chevy will do nothing and her extended warranty spells out they do not cover the cats. They don't do emission testing in my state and when monitoring the data I can say that they are not failed but borderline so I am in no rush to replace them. About every 1k miles or so her check engine light might come on so I gave her a $12 bluetooth OBD II adapter and she shuts it off with her phone. I just ask her to look at the codes and if it is anything other than a p0420 or p0430 for the cats to let me know.