The duration of the movie key was usually about a month. To be specific, the key was valid for about 28 to 32 days. Before the official pre-sales of the movie, a release notice would be issued, which would specify the time limit for the key. For some of the top films, especially those that were released during the Spring Festival, Summer, National Day, and New Year, they still had a high box office performance after the key period ended. Therefore, the film company would choose to apply for an extension key to extend the screening period of the film and maximize the box office potential.