As someone who's grown up speaking Mandarin at home while living in an English speaking country...I can tell you that, at least for me, there's no end to learning the language.

I think it's great for people to learn other languages from a young age and Mandarin is the language most people in the world speak, though the concentration of the Mandarin speaking people are in China I imagine...so it's certainly a useful language.

Actually, hand writing Chinese characters and doing Chinese calligraphy can be a fun form of art and language development.