An average of about three months of residential treatment seems to be effective. The optimal treatment time seems to be similar in non-residential treatment, suggesting a combination of residential and non-residential treatment might be effective over that time. But completing the treatment program and actively participating seem to be more important than treatment setting or length.
Dopamine is the neurotransmitter that is responsible for motivation and reward, and therefore it is a crucial neurotransmitter related to addiction. Drug abuse causes the release of surges of dopamine, and these in turn produce feelings of euphoria, followed by cravings, major reinforcement of the same behaviors, and compulsions to repeat whatever behavior produced the surge.

Addiction is a complex but treatable condition. It is characterized by compulsive drug craving, seeking, and use that persists even if the user is aware of severe adverse consequences. For some people, addiction becomes chronic, with periodic relapses even after long periods of abstinence. As a chronic, relapsing disease, addiction may require continued treatments to increase the intervals between relapses and diminish their intensity. While some with substance issues recover and lead fulfilling lives, others require ongoing additional support. The ultimate goal of addiction treatment is to enable an individual to manage their substance misuse; for some this may mean abstinence. Immediate goals are often to reduce substance abuse, improve the patient's ability to function, and minimize the medical and social complications of substance abuse and their addiction; this is called "harm reduction". Best Drug Rehabilitation Graduation
Research the history of the Treatment Center or facility.  What is their success rate?  Can you find any medical recommendations for them online from members of the established rehab or medical community?  How long has the Center been in operation?  Is their leadership on solid ground?  Are there any signs of financial corruption associated with the Center that is readily visible on the Internet?  It is your responsibility to dig for this information.  If you cannot find any information about a given Treatment Center online or at your local library, move on to the next Center on your list! 3 Stages of Drug Alcohol Rehab-How It Works