Blinking helps with lip sync. It helps draw your eyes away from the mouth for a moment and makes the character more lively.

When I added blinking into the my last animation, I went by feel. Playing the animation and inserting key frames about every time I blinked while watching it. This time I needed something more scientific and less time consuming. So I went over to Wikipedia.

I found out eyes blink about once every six seconds. My frame rate is 24 frames per second. Just to make it easier, I rounded this off to blinking once every eighty frames. I set a key frame for half open and fully closed to simulate the blink. Then copied and pasted the two frames every eighty frames along the way.

Making this one of the easiest things I've had to do in flash lately. Gotta love it...