Do O2 sensors wear out?

So in the past I have never changes an o2 unless it died. I always hear parts houses and o2 manufacturers saying they age and affect performance and should be changed on an interval. So whats the GRM hive say, do they, work or not work, or do they age and gradually performance drops.

Im finally doing some maintenance on the old dodge, its got about 300k miles and very little maintenance, and the mods on the vette are about to gut much heavier and I want the old girl to be reliable as possible, so when the vettes down I dont have to worry about getting to work.

Should I change them preventatively, they arent cheap but not expensive, bout 60 bucks buys me two OEM upstream sensors. Normally at this price id just buy them and not think about it, but between the front end parts and maintenance items its getting up there in price. 300K miles requires catch up on alot of deferred maintenance.

To the question at hand, they do wear out.

absolutely. they can be bad long before the computer complains about them, affecting fuel efficiency, idle quality, power... You can really have lots of other problems; vacuum leaks, dull MAF signal, coolant temp sensor out of spec, etc etc. And the ECU can correct for them by using an accurate O2 signal. If it hasn't got that, everything else had better be right!

They do wear out, but if they aren't throwing codes and its running alright and getting normal gas mileage, I wouldn't make them a high priority item.

On my old XJ Cherokee the upstream oxygen sensor was a 30k mile maintenance item. Pop a new one in, fuel economy would jump to over 20 mpg, by 30k miles later fuel economy would be down around 17 mpg.

Oh my yes O2 wear out. They not only get slow but they also drift away from stoich.

Chrysler cares so much about sensor drift that they calculate it by checking the difference between the front and rear O2s during the period where the engine is running closed-loop and the catalyst hasn't lit off yet. Rear O2s generally last a lot longer than fronts because they see less heat.

Chrysler also does interesting things like biasing the ground up by 2ish volts, so they can tell the difference between running lean and a failed sensor/wiring shorting to ground. Which is almost always the sensor shorting to ground (heater circuit), because Chrysler has engineers that are good at their jobs and bean counters that are also really good at their jobs.

They don't 'wear out' (no moving parts, duh!), but do become contaminated and degrade.
They are after all, exposed to live hot exhaust gasses.