Here is a direct quote from XLN support regarding redemption codes and time limit.
"Thank you for contacting us. You can redeem the products one at a time and use only the ones you have redeemed - there's no time limit. However - the offer is only for the currently available products, so you will not be able to redeem products that are released in the future."
So for a guy like me (who owns all the current kits for AD2) the 3 new kits I'm allowed are null an void. I can get the only two kit pieces I don't have, but that's it. And I can get 3 MIDI pack since I do not own about 20 of them.
Not complaining, just thought I'd at least address the question (awhile back) about timeout for the XLN redemption codes.