Will an excessive rich condition during part throttle driving foul the O2? (BLM 108, INT < 128 and rodent killing exhaust on cold startup)

If it does get fouled, must it be replaced or will it clean off when the rich condition is fixed?

What happens to the BLM in stock vehicles as the O2 gets too old. Do they increase, adding fuel?

 

Run one long enough and the carbon will be so thick as to never wear down again, and then yes it is junk. *can* an O2 con bak to life?. Sometimes yes, and sometimes no.

I have yet to see on fail from age.
I've heard of them going 200,000 miles on a well tuned car.
If not poisoned (which kills most of them I've seen), then they generally fail by going open, and setting a code 13.