RichG: Are you saying you do? Wow!
I've forgotten my Spanish, and everything is now either English or Japanese. -Or the occasional mix, some of which is intentional.
I lived near Osaka for 4-5 years after studying "proper" Japanese in college. Pretty much fluent in both, although it is easier to speak whatever dialect the people around me are speaking.
Mrs. Kid's die-hard Tokyo Japanese, but I'm winning her over to Kansai language/humor (in an effort to avoid forgetting it?)
Oh, and I dabble in English. I think it's cool how thinking in Japanese uses a different side of my brain from English. Freaky.