CATS - do they go bad?

[brp987]

I got a CEL on my 986 S. I hooked up my durametric and got the code but don't remember it right now. I looked up the code which basically said a CAT isn't doing anything. There weren't codes for the O2 sensors. There are 70k miles on the car. The front O2 sensors have 30k miles on them and the rears maybe 10k miles. The CATs have had an easy life - no AOS or IMS blowouts. So, would a CAT really go bad with so few miles?

I collected front /rear O2 sensor output data and put it excel, but that only added to the confusion. The signals rapidly oscillate. There needs to be a way to average the signal over time.