Humans blink once every five or six seconds, and each blink lasts about one-sixth of a second. If you add it up, you blink more than three million times per year. The main purpose of blinking is to moisten and clean the cornea and the conjunctiva, two membranes of the eye. In fact, your eyes would dry out if they stayed open all the time. But the eye also blinks if an object or person approaches quickly.