Depends on the shoe, but I rarely get more than 3-500 miles. Just tossed a pair with only 3:16 on them, but they were worn down on the heel, and had started to make me excessive fatigue after even short runs. I got 500 from a pair of Hoka bondi 7’s. I’m pretty hard on shoes, I have an aggressive wear pattern due to a shorter leg. I try to compensate by buying shoes on sale and rotating them as much as possible. But your milage may totally vary. But replace em when you think you need to, many ultra runners get 1k +