I found an interesting interview on the internet from The news source of the Harvard Graduate School of Education. The interview is with Professor Catherine Snow who has a Ph.D. from McGill University and is "an expert on language and literacy development in children."
In the interview, she states exactly what I have always felt, but she does so with authority. She says, "there is no critical period for second-language learning."
It is a very interesting interview, and I encourage you to read it for yourself.
The interview can be found here.