1. A computer-implemented method, comprising: storing, by file system software implemented on at least one computing device, expiration policies for at least some files within a file system in file system metadata maintained by the file system software, wherein the file system software is configured to provide for creation of, management of, and access to the files within the file system, wherein each expiration policy is specific to a respective one of the at least some files and specifies one or more metrics for evaluation to determine whether the associated file is ready for expiration, wherein the file system metadata includes information that the file system software maintains on files stored in the file system, wherein a specific expiration policy associated with a file is stored in a portion of the information that the file system software maintains on the files stored in the file system that is specific to the file and that also includes location information for the file; wherein said storing, for said at least some files, a respective expiration policy for the respective file in a portion of the information that is specific to the respective file and that also includes location information for the file, enables each of the at least some files for moving or copying to another location while maintaining its association with its respective expiration policy; and evaluating, by the file system software, the expiration policies stored in the file system metadata, wherein said evaluating produces a result indicating at least one file that has passed an expiration date for the respective file according to the expiration policy corresponding to the respective file.