Though a battery cannot be stored for long time, it can be stored for a shorter period.
Once a seal is peeled off, the battery starts ‘breathing’ and therefore gives of energy, even if it’s not used in a hearing aid. The battery therefore won’t last until the expiry date if the seal is removed.
However, you may lengthen battery life a little bit by putting on the seal again, although this won’t guarantee maximal storage. Always use the same seal. Scotch tape may leave glue residue on the battery, leading to improper contact.