Looks like your good. Says right here got Regional Upgrade Certs: "Expiration Date: Certificate expires twelve months from date of issue; all travel must be complete prior to certificate expiration date. Certificate may not be extended, reissued or returned for credit under any circumstances."
http://www.delta.com/content/www/en_...tificates.html

But call the elite line and ask again (even write down the name of the agent - - then you should be double sure.