sprman24,
I am involved in a lot of interventions and do a lot of referrals for detox and rehabs and can help you a bit on general information. Detox's are short term... anywhere from a few days to a week up to a 28 day stay. Some consider a 28 day stay a rehab when it really is just a start!
The longer the toughest cases can stay in a QUALITY long term rehab facility followed by a serious and diligent program of outpatient treatment the better their odds are for staying sober.
Being physically seperated from the drug of choice has the benefit of the brain being able to heal and better able to think rationally and make responsible decisions about their life's choices.
Quality treatment... good therapists, groups, AA 12 step etc... over time forms new habits and new thinking on subjects long twisted by abuse of substances.
Another book you might like and find helpful is No More Letting Go ... it is how you can raise the bottom for the addict while still creating healthy boundaries for yourself.