Dont even bother asking that question, there is no right answer.
It will vary with every car and every driver. Like I have said in the past, I have friends running 12s with 180k miles on stock original motors. While poeple like me may be on thier 5th motor at 170k miles
It depends on how you maintain the car, how hard you race/drive it, and how lucky you are. I have bad luck.