Theres no way to answer that question. It comes down to your expectations. If you are playing the same games it will last forever. If you are constantly updating your gaming library with newer games, it comes down to your expectations of performance, and what other components you're pairing it with. Particularly the video card.
Forget the video cards as they will be easily upgraded for me. I have no problems with them because their is no need for getting new mobos because of new sockets. But seeing as Haswell and Sky Lake are up next for Intel do you reckon it would last a good few years?