I have been immersed in Spanish on many occasions, and just got back from 10 days in a Spanish speaking country. I can communicate well, and served as a translator for my English speaking friend, but still am far from being "subconsciously" fluent. I am still pretty worthless when people talk fast or not clearly. I still don't pick up on Spanish i hear without my full focus on it.
How did you conquer the final fluency hump? Getting frustrated over here! Total immersion isn't possible at the point.