147k on OEM plugs.

[k1xv]

Modern plugs do not "wear out". Rather, they keep going until they fail, usually due to gas leaks between insulator and shell. The recommendation to change them is to replace them before they are likely to fail.

Same with computer hard drives. Either they work, or they fail. They do not "wear out".

 

[chorty]

The end of the electrode burns off eventually. Photo in post #1 shows it

 

[zzyzzx]

That old plug looked like it could have been cleaned and reinstalled. Unless I'm missing something, it didn't even need to be regapped. I would almost expect that for a V8 or maybe a 6 cylinder engine, but not for a cylinder engine.

 

[super20dan]

i went 187k on ourh highlanders oem plugs. car was still running smooth