Grains will store for years, even decades, if stored properly (see below for proper storage recommendations).
For example, grains were found in the Egyptian tombs that still sprouted! Not all grains are the same, however.
We recommend good storage practices and rotating through your grains, always using the oldest first.
Chia, since it’s so fatty, is more likely to go rancid. It will last two to four years. Hemp hearts can be stored for about a year in the fridge and a few months out of the fridge.