On Sunday, April 14, 2019 at 8:58:19 AM UTC-7, wrote:
One of my sons, who is pretty big and strong,, rides an S-Works Tarmac CF frame (about a 2006 model or so) with the plastic (polymer??) bits in the forks and the chainstays. It seems to be in excellent condition. Have you ever heard of any problems with the plastic suspension bits disintegrating or breaking after a long time? Thanks!

No and I always look at those on my riding partners bikes. I don't really thing that they do anything.