Hi! My Boyfriend Was A Meth User From The Time

Hi! My boyfriend was a meth user from the time he was 12-15 until a month ago (he's now 27). He's experiencing auditory hallucinations and severe cravings. The paranoia and hallucinations have persisted even though he's been clean. How long does it generally take for symptoms to decrease? Does the brain begin to heal itself? Is it possible it's permanently damaged?