Well, on average I'd say around 6-9 mos is more normal, but it's very much an individual thing. Production crosses tend to lay bigger ones sooner, but they also burn out sooner and aren't truly dual purpose. I like the old breeds, that take longer to grow up, but also last longer and are more hardy. JMP (just my preference)
I have a combination so you know, some Golden Comets, some old standards. I like covering all my bases!