If we're going by anecdotes, my last Noctuas showing signs of failure (I had 6 of them, one was ~200rpm slower than it should be, one took a several seconds longer to start spinning from a stop) about a year after the end of warranty was partially why I retired them. Same with the set of Noctuas before them (apparently my first set was from 2010). I suppose they all technically still spun so they were still usable, just not to original performance; still, hard to be too upset about the product making it through the long warranty period without issue.

But my Arctics that was installed in the same case that ran for the same amount of time are still chugging along strong, and those are about as cheap as fans get. Different load/use case though so it's probably not a fair comparison.

These days, I really think the competition has caught up or passed Noctua.