Why aren't my dreads growing and getting longer? - Dreadlocks FAQ's
Generally the hair grows at exactly the same speed after it's dreaded, but the dreads gain length slower because as the hair grows it zigs and zags horizontally or back and forth in the dread, and this takes up much of it's length. Thicker dreads are effected more by this than thinner dreads.
During the first months the dreads will be doing a lot of tightening. As they tighten, they draw up and compress. This causes them to stay the same length or even loose length, even though the hair continues to grow.
When the dreads are mature they will begin to gain length faster than before, but still not as fast a un-dreaded hair. Thinner dreads will always gain length faster since there is less back and forth due to the smaller diameter.
If you would like your dreads to gain length faster I'd recommend eating more raw fruits and vegetables. Also, in our online store we now have DreadHead Supa Hair Growth Supplement. It's a custom formulation that includes MSM and Horsetail Herb for those that are really impatient and want the fastest possible hair growth. =]