Alej64

GTXJackBauer
 
You could lower them via fan curve through PX1.

I can. But I wonder if it's a factory bug or feature that it doesn't stop fans by default. Should it? Maybe I have some background activity or malware miner (though antivirus is always on). Does that have any significant effect of fan lifecycle?

Fan don't need to be turned off to preserve them.  They can run for a very long time before they give.  For example, my PC runs 24/7 for many years.  Have put all kinds of load on it like Folding@home and gaming of course.  Most of the parts are 5+ years old.  Still trucking along but showing it's age. (8 years)