Spending more time in recovery means that a person has the opportunity to understand the underlying cause of their addiction. When a client arrives at a rehab center, detoxification(detox) is often the first step that is required. After the client has completed detox, they need some time to adjust to the daily routine of the residential facility. After that point, the treatment process begins.
Detox and adjusting to the treatment center can take a couple of weeks on their own. If a client is only signing up for a 30-day program, they are not leaving much time to learn skills which are going to help them make lasting changes in their lifestyle or help them resist the urge to start using again when they have to cope with life stressors.