Define signs of wear ?
That is a given to me... Once a system has been used....
If used for decaf then even more so..
Looks Well worn; would be more of a concern ;)
Totally Dull or blunt or Stuffed would different again..
It is not like there is a defined scale when one can look it up and say yep...That is a 3.75 grade out of a 5.00 ;)
I have seen some burrs last for ever and other get dull much sooner than expected... But ask any Sponsor to provide full warranty on the burrs for ware... They are a consumable and cheep to replace...
If they fell apart or fractured for no reason... I am sure most sponsors would have a close look and may come to teh party if a manufactures issue... .