Hi According to the manufacturer that type of emergency light should last on between 20 and 24 hours; As for the charge stored in the lithium-ion battery (that I interpret) at full charge it will keep 80% of this per year (they remain long with charge) and if they have half charge, it can maintain 95% of its original load per year (room temperature). This is in the best conditions, you should see the status of the battery, its charge and the type of led circuit it has. regards