I don’t print any abrasive materials at all. Pretty much only normal PLA and PETG.
I noticed, that my print quality gradually went down quite a bit, especially in the last few prints. I had a lot of stringing, weird blobs, and scarred surfaces.
Now, the print quality is as good as it should be!
They are dirt cheap. You can get a set of 10-15 generic ones, in different sizes, for only a few bucks. Don’t forget that they are consumables.
Wouldn’t it be better to replace them regularly by some metric, uses, time, etc?
Yes, but that is also going to require a ton of extra effort to track and assumes the nozzles themselves wear consistently. There would probably also need to be modifiers based on materials used, and even brands. For a professional print farm or a business trying to squeeze every last dollar out of the operation, this might be worth it. For a hobby where we expect a lot of waste? Eh, fuck it, just replace it when prints start going south.