Teams must continuously improve processes within their control.  Working on a single issue for 6 months could become tedious.  The team would need to expand their goals, keep improving aspects of their process and apply the skills to other processes.  In my experience, if everyone in the unit is engaged in improvement, it will take a minimum of two years for it to become part of the unit culture. Then as new members join, the culture of improvement is inculcated into their behavior.  

I agree with Diana and would ask the following. What specifically has signaled that change has actually taken place? You mention 'displayed charts', so I would like to know about how you evaluated this.

Diana and William, thank you for sharing your submissions and experiences. Site QI teams adopt changes for testing from consolidated change package harvested from previous QI efforts , on few patients, for a period of three months. If the change works for a team after that action period, they adapt it and scale up the QI efforts for the particular process to cover all patients in care. The site-providers are encouraged to track thier performance using documentation journals and displayed charts [simple run charts that incorporates a median to determine if the change was significant] as part of thier self evidence based evaluation. This might take a year or so depending on the team's commitment. There should be a six points consistence in the performance above the median line to declare an effective change. This does not mean that the team drops focusing on the process. It becomes a routine to monitor the improved process and ensures maintenance of the continued good/best practices. Graduation, therefore here means the team change thier focus to another process that needs improvement and initiates QI projects.