Catalytic converters keep going bad

My 2500 HD 6.0 gasoline engine is burning up catalytic
converters left and right I've done had to put two sets of
cats on it within two years the truck runs fine don't know
why it's burning up cats left and right. I have noticed that
my ac doesnt blow as hard as it did at first and ive replaced
everything to do with that. And my passenger side
headlight was burning so hot that the wires got brittle and
had to replace the wire. I'm not sure if it's all connected but
i could really use some help