If you are buying 12 codes, activate all 12 codes with the 12 mac addresses so they are linked. You can then deactivate the codes until needed. You wont lose any time on the codes while they are deactivated.
I just think when it goes live, they will be extremely busy. At least this way you will already be linked. Thats just what I would do but you can also just wait it out and see what happens when free trial ends.
Hope this helped a little.
