I bought my first pair 8 months ago. Not a single "nub" has broken off as far as I can see.

I never wear my pricey Keen sandals or cheap flip-flops anymore. These slide on easily and stay on comfortably for lengthy walks, unlike flip-flops.

They do take some getting used to initially as the nubs can feel uncomfortable; I never notice them now.

I'm buying my second pair as these are looking a bit dirty as they've seen a lot of beach/dirt wear.