I tried to find the official ruling on when cards were legal for tournaments after their release. I seem to recall that as soon as they were released they are legal ruling last year. What's official?

Days of Ice and Fire FFG said that 30 days was the standard, they had made a special exception for whichever pack had come out because it was at 26 or 27 days.

Now your local TO will always have the choice about what they want to do for local and regional tournaments. In the CCG days two weeks seemed to be the norm, I think to ensure everyone would have access to the cards.