Since it's soy sauce, Tamari is high in sodium. That's why it's a good idea to store your Tamari in a cool place. You can even stick it in your fridge (make sure you don't freeze it, though). Also, if you don't use Tamari often, try finding one that comes with an airtight lid to keep out humidity and oxidation. For freshness purposes, I recommend getting small bottles when possible. Please note that you should never reheat opened Tamari. Doing so can kill off certain nutrients and vitamins. Finally, keep it refrigerated and eat within three days for best results once opened and cooled down.