If you're talking about outgrowing their baby feathers, that seems to be an ongoing process while they grow up; at some point all their adult plumage is grown in and that's that for a while. I think molting is on an individual basis - my EE's molted at around 9-10 months, in the fall of last year. On the other hand my BR's, the same age, still have their original set of "big girl" feathers (tho I think they're getting ready to molt, but at this point they're nearly 1 1/2 years old).
You'll know when it looks like a chicken exploded in your coop - more feathers on the ground than you ever thought were on their bodies.
Enjoy your chickies!