Duration of animation

Based on research by Nielsen Norman Group, the optimal speed for interface animation is from 200 to 500 ms. If the animation lasts less than 100 ms, a user is not able to notice that something has happened, and if the animation lasts longer than 500 ms, it's very slow and boring for the user.
For better user experience use short duration for such effects as fading, hovering or just elements which traverse a small area. And use longer duration for large moves and complex animations.