My left hand was broken and healed improper, when is the best time to break it and cast straight?

My left hand was broken and doctor put cast on it, but it didn't heal straight. Since it has not healed perfectly and there is 3 more week to heal perfectly, I want to know when is the best time that doctor can break it and redo the casting process. Some people say it should heal perfectly then doctor can do that. But does it make harder to do the whole process?