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 have had this about 6 months and it has never fallen off the mirror. I love how it sticks out from the mirror. Very convenient. I thought it would bother me aesthetically but it blends in well enough that i don't find it offensive. I use it every day. Highly recommend.