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.
I just experienced this for the first time. I has having to print slower and slower to get the filament to flow enough not to print skippy and stringy. Finally, the gears in the print head started skipping. I took the whole print head apart and found nothing wrong. Switched to the spare hot end that came with the printer and its printing like new again.