Bosch had (or has) a web page with a graphic taking you through the evolution of oxygen sensors and the increase in lifespan. Check the first reference cited on this Wikipedia page.

It also showed a shift in their replacement recommendation interval. The first ones, unheated, were supposed to last 30K, and the later heated sensors indefinitely. Last I looked, they changed "indefinitely" to 100K, or something like that, for the heated sensors.

I interpreted the revision as a concession to allow for the mileage-based changes an engine undergoes which result in contamination of oxygen sensors, that otherwise would have lasted "forever."

Personally, I do nothing in the way of proactive oxygen sensor maintenance. It will take a reduction of fuel mileage, a noticeable performance problem, a flunked emission test, or an OBD code set, to bring my attention to the lambda sond.
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Art Benstein near Baltimore

A dog teaches a boy fidelity, perseverance, and to turn around three times before lying down. -Robert Benchley