What type of electrodes are we talking?
I ask because if it's FCAW there may indeed be a limitation once the package is opened. We use Lincoln FCAW electrodes and the manufacuturer recommends that once the package is opened that the product be used within 7-10 days unless you take it off the machine and store it in a protected manner.
SMAW our 7018 are always in a temperature monitored oven so those have any issues either.