Amazon calculates a product’s star ratings using a machine learned model instead of a raw data average. The machine learned model takes into account factors including: the age of a review, helpfulness votes by customers and whether the reviews are from verified purchases.
I bought a pair a year ago and they're still in good shape, except the grip on them isn't what it used to be for obvious reasons. If you use them a lot, expect to buy another pair down the track. Really great thumbstick, would recommend!