I submitted my code waaaaay back when FFXIII came out and that code is already attached to my SE account, so I am assuming I didn't need to re-enter it again. IMO, I would still enter just to be sure, but I also lost mine so hopefully they still see it.

I also re-applied even though Alpha testers weren't required to. Some things have changed since I applied for Alpha and by mid February I'll have different ISP.. not sure if that really mattered a whole lot, but I pretty much updated my application.