[andylaurel]

I don't think age has a whole lot to do with it (after the 2nd critical period.)
My Japanese has increased 10 fold since arriving in Japan 18 months ago and I attribute that to;
a)My Japanese girlfriend only speaks to me in Japanese.
b)My Japanese colleagues speak to me in Japanese.
c)I spend a respectable amount of time studying.
d)I have a reasonably good ear for languages.

Having said that, I have students who are simply not talented at languages. This is ironic given that they are studying at an English School. If you fall into that category, then the road ahead will be bumpier.