Usually between two and five years, depending on the type of the watch, its dimensions and the quantity of energy requested by the different functions. For instance, a chronograph will have a higher energy consumption than a watch indicating the hours and the minutes only. Certain types of watches feature a power reserve indicator: when the seconds hand starts jumping every five seconds, it is time to have the battery replaced by a qualified watchmaker. Special lithium-iodine batteries reach a theoretical lifetime of ten years.