To publish a file without expiration, use the publishBody(_:) method. The URL will remain valid and the file will be accessible forever.
The basic steps are as follows:
Upload the file as an object body.
Publish the file with the publishBody(_:) method.
Note that a user needs to be permitted the KiiACLObjectActionRead action on a KiiObject to publish its object body (Once published, anyone can access the object body with the URL). See Setting a KiiObject's ACL for more information about the access rights.