...it depends. By definition, Methadone detox takes place over less than 180 days. The patient is progressively weaned over that time. Methadone maintenance, on the other hand, is more than 180 days. The decision is made by the patient, physican, counseling and social services over which route to take, and the best outcomes occur when everyone on this team takes an active role throughout the process.
Depends. Completely depends why its being given. For chronic cancer pain it might last for the rest of a persons life. For a semi-acute pain episode it might last for a few weeks. For addiction treatment it might be a month-long detox and Methadone taper versus lifelong maintenance depending on a patients cravings for recreational drugs.