Signs of the MBD will always remain (bent legs, healed bones and such) but If you have got it under control your Cham will be able to get around as good as normal (considering what it went through) Bones healed, and act more like A normal Cham would do. Keep the suppliments and lighting up abit though so the Cham wont fall back into the realm of MBD.
An xray is the best way to see how good his bones are. Also as Titan said how he is getting around. It was 7 months for my guy and I still keep a close eye on him. Is his grip strong on your finger? Does he move around without losing his grip or shaking? I am not sure how bad it was in your guy so its hard to tell you what exactly to look for but better to keep the treatment going longer than stopping too soon.