Fyi, it does seem that when you book a flight and want to use SWUs now that Delta is reticketing very quickly. There've been a few other postings where the SWU was processed within days of ticketing even though the flight was months out.

Recent experience of mine when I booked an intl itinerary a week ago:
Agent could see the SWUs in my account, copy/pasted the SWU numbers to the ticket and told me which ones he used so I could keep track and said it should be reissued with the upgrade processed about a week before departure. However, I received the ticket reissue overnight while I was still within the 24hr cancel period. Nice that they're doing it quickly, but bad if I wanted to cancel since I think once the SWU is 'closed' its basically gone if you need to cancel the ticket.