I had this discussion with a fellow shul member.
He has a box of shmurah matzot that he left in the closet from last year. When he opened it up, recently he noticed that they were stale. He says that since they got moist, they became chametz and cannot be used. He further pointed out that since all matzah boxes stamp the year it was made, this means that one can never use matzot from one year to the next.
My thinking - as long as the matzot never touched chametx, why would there be any problem using them. One of my friedns bought cases of matzot after Pesach was over because the prices had dropped significantly. The boxes were never opened, and on Pesach she had 1 year matzot. Some were a bit moist, so she put them in the oven for a few minutes and they were crisp and fine.
As for my friends concern about it being moist, I don't see how this is different than the concern with gebrokts, and then, the matzot are completely soaked in the liquid. Yet, many people eat gebrokts!
Who is correct, here?