Replace O2 and AF sensors as PM?

[scrubolio]

With the 25% off sale going on right now at toyota parts, i was thinking of getting the 4 sensors just to replace the original ones on the car or keep them for when they do fail.

Smart idea? or just wait until they go out?

I have 140k miles on the ODO

Thanks!

 

[bloc]

I did the front sensors at around 175k and saw no noticeable difference in fuel consumption, which tells me the old ones were still pretty accurate.

Not sure I'd recommend it to someone unless they were chasing an issue.