Originally Posted by Often1

Looks to be slightly more complex as an overall matter, but return does appear to be more flexible (cut & pasted from delta.com):

Changes to Award Ticket Travel must be made at least 72 hours prior to the departure time of the flight being changed. Award Tickets booked within 72 hours of departure are nonrefundable and cannot be redeposited or reissued unless prohibited by local law. No changes will be permitted to the originating of Award Tickets booked within 72 hours, however changes to the return are permitted if the return flight is not within 72 hours and the change is made at least 72 hours prior to the departure flight. Fees apply for any changes. Please visit delta.com/fees for our current fee schedule. Changes to the return portion of an Award Ticket is permitted at least 72 hours prior to the departure flight. Taxes and fees will apply. Changes to Pay with Miles tickets are determined by the fare rules of the ticket purchased.