Only if you permanently keep up your practicing. I met a woman who had studied asl and developed some skill, then spent some time away from it (a number of months) and it was horrifying to see how much she had lost (especially to her!)
It was sad to watch her sit there and realize she couldn't remember to say much of anything, but in a way I was glad to have it made clear to me: all the work I've done learning this stuff could vanish really fast if I don't keep up with it. I have every intention of keeping up with it, but if something comes up that requires walking away from it and returning later, I'll know what the consequences will be.
It's scary to see how fragile language is. If you use it every day, you keep it. But that "use it or lose it" saying is really really true.
