Originally Posted by
MSPeconomist
If you wait, there's a good chance that the seat you want will be gone. The sooner you do the seat change the better your options are (except perhaps if you're trying to move up into EC, exit, or preferred seats as others are upgraded).
I'd be annoyed by the ticket reissue as I want to know when my ticket has been reissued so that I can submit for reimbursement the receipt for the ticket that was actually flown. I wouldn't want someone to notice a discrepancy and question it.
Agreed with the annoyance.
Another issue is if you're in a tight UG situation - you will lose any priority based on ticket issue date.
I think the OP would be fine to contact @DeltaAssist if he's not worried about discrepancies in date, as he's already been upgraded.
I have found sometimes that patience in waiting for EC seats pays off, as GM+ members will be cleared for UGs late, and I can take them closer to boarding, but there are certainly no guarantees..