For the expiration date issue, actually, in general there is no specific life time for salt bottles.
If you can store them appropriately, such as in a normal environment (neither too dry nor too wet), they can last longer.
In addition, there is another way to make sure if the salt bottle is still available or not.
We will suggest user to check the situation with the salt and the liquid in the bottle, if you can see the salt and the liquid exist “together” in the bottle, the salt solutions is suitable for calibration; if not, we will suggest user to purchase the new salt bottle, even though they have not been opened.
Welcome to download the more details from the following linkage,
Shelf Life of AZ Salt Bottle(58 KB)