That depends on what temperature the Graphics Card was running at during mining.
If you had temperature monitoring software installed such as HW Info, GPU-Z or MSI Afterburner then as long as the card wasn't running over 75°c or so then the components lifespan shouldn't be overly affected.
No, every electronic device has a lifespan and when you have run it for so many days with constant heat, the card won't last as long as a new one. But still it will do for two years I think.