In my experience with language learning, 'if you don't use it, you lose it'.
Are there any studies regarding re-learning a second language after [extensive] periods of disuse? In particular, I'm curious how the initial proficiency before disuse (e.g. Fluent, Working Proficiency, Beginner, etc.) affects the rate at which a language can be re-acquired.
I would imagine that if one was fluent in a language and then did not use it for several years, it would come back quickly, 'like riding a bicycle'. However, in my experience, trying to recover from a hiatus before which I had been at working proficiency is relatively slow.