The rim protectors included in my tire lever kit tore straight through and resulted in a scratched rim.
While that has some to do with technique; I have better luck using 3"x4" strips cut out of milk jug or oil/antifreeze bottle. It's usually HDPE and tougher than the rim protectors that come with spoons. Scratches are going to happen mounting tires by hand, that's what touch up pens are for.
How are you balancing them?