Chad, I believe it is 1" per year but on a 2" board 1" in from each side is 2" total so a year should be enough. That said, the longer you "cure" the wood the better. Even though at the thickness of a board it will dry in a year or so, it will continue to "cure" over many years. The longer the wood is cured the more stable and resilient it will be.IMO Pat