cat converter

What is your question?

About a yr ago, I replace the 2 cat converter and the senors (all) twice the engine light came on. the dealership said the cat are bad, miekie replace all parts,they didn't give me a warrenty, the first time the light came on was about 3months after the repairs,clears codes, anow the engine light came back on,the same codes,the cats are bad. my question are: why so long in between engines come back on? Whats your opinion on direct fit cat converter,and if any other problems can cause this issue. The truck is well maintian. Please help!!!!