Keep filing those applications
File applications with departments that accept them on a continuous basis.
One thing candidates can do while waiting for their next exam is file applications with departments that accept them on a continuous basis. Many of these departments will keep them on file for a specified period of time, or until their next exam. Often these departments will not do a public job announcement when an opening arises if they have a sufficient number of applications already on file. When this happens, only those who have filed their applications will be invited to test.