Extensions. If extensions are authorized in a development agreement, an applicant must request the extension at least 60 days prior to expiration. For development agreements associated with project permit applications, the development services director may grant an extension for up to five years if the applicant can satisfactorily show that, for a residential project, at least 50 percent of the residential units are constructed, or for nonresidential and mixed use projects, at least 50 percent of the gross floor area is constructed. All other requests for extensions shall be reviewed by the city council, unless another process is expressly provided for in the development agreement. In no case shall an extension be granted which would allow a development agreement to exceed 20 years.