The employer's need may generally be only for one year. However, the need, under the 'extraordinary circumstances' provision, may ultimately be longer than one year if the extended need could not be anticipated at the time of application.
Note: An example might be the case of a hurricane that destroyed a large bridge. It will take 11 months to replace the bridge. After the application is approved for this 'one time' occurrence, the employer demonstrates that the work cannot be completed in 11 months based on circumstances which did not exist at the time the employer first petitioned for the foreign national. The work will now take 14 months. The employer would file another application for the three additional months.