If you are referring to the signed urls for private data stored on Amazon S3, If files are publicly accessible they can be accessed with a simple url to the file: eg http://s3.amazonaws.com/[bucket]/[key].
However, they can be set to private in which case you need to provide a signed url to access the file.
Also, for the file downloads, you'd probably create a new url for each request with the url set to expire only a day in advance to protect your data. However, this does not expire/delete/remove your data stored on S3. It only affects the url to the file. You can go ahead and generate as many urls with different expiry dates as you require.