In all the early access games I've played, it's never lasted more than an hour between early access shutting down and official launch. I don't even remember if GW2 went down at all, they just pushed right into it. Only reason most take so long is because of a small network error or last second update/bug/server error. Don't worry, I'm sure they won't cut you off at 12 AM on the 26th and then make you wait 24 hours to play again lol