12 months is a good rule of thumb as to when the final result of the hair transplant is in.  That being said, you should be able to start seeing the results at about the 3 or 4 month stage, and then it should get stronger and stronger as the months move on.  Some people see results that improve after the 12 month period, so there is some variablity.  But give yourself a year for that game changing dramatic result!