depends how long you wear em and how hard you use em.
mine last for years since i wear sandals pretty much everywhere. i run several times a week now and try to rotate my shoes. ill have three or fourpairs at any given time.
i am having a lot of heel pain so im opting for all new shoes and they are so comfortable
ive bought sauconys that are like walking in heaven and adidas trail running shoes in the last three weeks. im planning on buying at least three more pairs in the next month or so.
there is nothing more comfortable than a new pair of running shoes.