cat converters

What is your question?

I replace the senors and two cat converter 11 months age. About two weeks later the engine light came on again the dealership said the cats are bad,the dealership wipe the codes out. I waited for the engine light to come back on,so i may take it back to miekie, it just came back on now.(11 months later)My question is, is it the cat. converters or something else triggering the senor. the price at tilden is $650.for parts and $150. for labor.Tilden is going to put on direct fit,parts not universal parts. Please,give me the best detail you can,of my problem and parts i am going to replace. Please help!!!!