Quoted from Pesmerga:

Can you help me understand when pop rings needs to be replaced? Mine seems always ok! Can I try this method of polishing on my old rings also? Thanks

Quoted from Elicash:

In my (brief) experience, pop bumper bodies and rings don't need to be replaced unless they are broken.
I recently rebuilt my BSD pops and the new bodies from Marco were very inferior. After the rebuild, every time the pop was actuated the ring would shear off a tiny dusty shards of the plastic. the whole pop bumper area become covered in white shards and dust.
I ended up cleaning up the old bodies and using the whitening technique with peroxide and sunlight.
As far as rings go, if they're not bent or broken, why replace? Just clean and polish. I have read a million posts from people lamenting after-market metal parts that are totally inferior to the old original items. I have had this experience with flipper rebuilds, post screws, etc. not to bag on marco or pinball life, but I just dont think the new metal parts are made as well as NOS or just old parts that are not worn.