As with all other mobs, I thought that naming an Ender Mite would cause it to never despawn. This would be particularly useful for a new end farm design, since endermen seem to run at/attack Ender Mites. However, after about 2 minutes the Ender Mite despawned anyway. I tried naming it several different things, including Jeb_ and Dinnerbone; I tried standing at various distances from the Ender Mite; and I tried having it in a minecart, and standing on different blocks to no avail. No matter what I do, or what the Ender Mites surroundings are, they always seem to despawn after ~2 minutes.