Angel is right, they don't all grow back but I have never had one that didn't, at the very least, vastly improve, became less sensitive and less problematic. In honesty, I've only had two that didn't end up, eventually, with a completely normal beak. Those two ended up with about half as much again as what they had when they joined me. It does, however, take a long time and depends on how healthy they are and how well they respond in their new environment. Don't expect anything too much for at least six to nine months as far as new beak goes but they seemed to de-sensitise in three to four x