Anyone had these for years; are they still preventing weeds/grass from growing up through the ring?

Yeah, since they're porous enough to let water through, grass can grow into them from below or above. It's not a huge problem, a small clump here and there every year. If you left it forever it would get totally overgrown so every couple of years I pick them up from the soil and lay them out on the patio for a few days until the grass dries out and dies, then pull off the dead grass and replace the rings.

I've had these for at least 10 years now. Sometimes weeds get through, but it's minimal compared to mulch. Also try rings made from corn stalks.

I have had them for years and after a while weeds do start to grow through them. The last one that I put down 3 years ago weeds starting growing up through it this past summer. I just dug it out and replaced with another ring. I think over time the cloth lining underneath falls apart and this allows the weeds to grow through.

The product is meant to deter weed growth. There are many variables that can impact weed prevention.