How long can a person live on ECMO?

Can you explain the duration of a person's life expectancy while undergoing ECMO treatment? Is there a standard time frame or does it vary based on individual circumstances? How does the severity of the patient's condition and the reason for ECMO use factor into this equation? Additionally, what are some of the potential risks and complications that may arise during an extended ECMO stay, and how do medical professionals weigh these factors when determining the duration of treatment?