You might think metal doesn’t expire! However, the metal or filler material that is used to make these welding rods or electrodes does expire. This is probably due to the moisture that they have retained and been exposed to with time.
This is quite a speedy process depending on the environment they’re kept in which is why most manufacturers suggest that you use them promptly once unpacked. A good way to prevent this from occurring quicker is to keep your rod away from moisture and to keep it dry.