The car with cats actually initially failed the NOx emissions, I believe the egr valve needed to be rebuilt/cleaned.

Basically my point in all this was that over time cats become ineffective, and the emissions standards that are out there are really based on being able to pass a vehicle after the cats are mostly not doing anything as long as the rest of the vehicle is in good condition/maintenance. CATs are very effective in reducing pollution during the 1st 7 years and then you can watch the emissions creep up year after year if you're in a place that actually measures emissions. Stories I've heard first hand of people who have had to replace CATs to meet emissions actually tends to be somewhere around 15 years, but other things that are easier & cheaper to to do, to get a pass, start at around 10 years.

 

My car was built in November 2005 so the factory cats are almost 12 years old, though the car's only done 83k miles. I wonder how many lives my cats still have left in them.

 

Well, this cat is about to have all 9 lives take out of him if he keeps doing this:

 

I'm wondering why that cat still as a life left

 

Basically what a cat does is complete the combustion process. When fuel doesn't burn completely you get nasty stuff like CO, NOx, hydrocorbons. A cat converts these into CO2, N2 and water. A well build engine running high octane fuel can complete this in the combustion chamber with less of the nasty stuff coming out the back.
About 20 years ago, Hot Rod magazine did a story about a engine they build for I think was a camaro. They were in Cali so they tried to get it passed for emissions. No shop would touch it because it had no cats and they refused to pass it. Something about being afraid the government would come after them and take their license away. They finally tested it unofficially and it passed with flying colors.