My EEs have always been late bloomers as far as eggs, but such reliable layers that it doesn't bother me too much. I think they were more like 24-26 weeks. I was concerned about them, but a friend of mine said hers started later than her other breeds, too.
Full plumage...I think by nine months old, they looked like adults rather than pullets, but I didn't really pay attention.
They are beautiful birds. I didn't much care for muffs and such, just got them for the pretty eggs, but they've really grown on me. My EE roo has the classic red/black/green color pattern (but with the characteristic muff and body) and this amazing tail. It's no wonder he struts like that, he is a real looker. LOL