If the oxygen sensors have been in the vehicle for over 60K (up to 100K, which is the recommended replacement interval for OBD-II cars), they should probably be changed anyway.
Especially given how "fragile" the pre-cats are. Not that I'm suggesting that a worn out, sluggish oxygen sensor could cause a pre-cat to fail....I'll leave that to Bosch[1], but it is rather interesting, isn't it, that I got a code P1151 (bank 2 oxygen sensor not switching/lean limit), drove around with it for about 300 miles, replaced the sensor, and shortly after I replaced the bank 1 oxygen sensor, I got a P0430 (bank 2 catalyst efficiency below threshold).[2]
Then again, it's also rather suspicious that I made the P0430 code "go away" by cleaning the throttle body with the engine running[3], and then passed the emissions check with the lowest readings the car has ever gotten. I also replaced the bank 1 oxygen sensor, figuring that if the bank 2 sensor had crapped out, bank 1 can't be far behind.
[1] Bosch states that a faulty oxygen sensor can cause catalyst failure. Maybe they're overstating the case to sell a few more, but my bank 1 sensor was really wacked. Clear the P1151 code and it'd come back within two drive cycles.
[2] The catalyst monitor does not run if there are any pending or active oxygen sensor codes.
[3]
See my post about this here