It looks (if they are using the same technique as the youtube video linked in this thread) that once it has expired you either need to change the lamp or potent

It looks (if they are using the same technique as the youtube video linked in this thread) that once it has expired you either need to change the lamp or potentially replace the salt water with an aqueous solution of (very strong) reducing agent. Or you could be even use saltier water in the lamp to make it last (slightly) longer once it has expired.