I hope they slow down soon, because if they keep this speed up, they are going to be old and wrinkly in a few years and die. ;-)
The two biggest dorotheae grew yet another pair of leaves over the winter (others finally started, too) and now I can proudly say, that they look like dorotheae!
This is the most beautiful of them all:
Lithops dorotheae on April 10, 2009