The average Lithium battery in awireless smoke and heat detectors will probably last somewhere between 1 and 3 years. Battery life in wireless sensors can vary greatly. The type and model of wireless sensor is the primary contributing factor. Refer to the manual for your device to determine what the manufacturer states the average battery life will be.
Another factor could be the type of battery used, such as alkaline vs.lithium. Usually, lithium batteries will last longer, and most modern wireless smoke and heat detectors now use them. Each wireless sensor will have specifications with regard to the batteries that can be used. DO NOT USE BATTERIES NOT APPROVED BY THE MANUFACTURER.
Frequency of use is also a contributing factor to the length of battery life of wireless smoke and heat detectors, or lack thereof. For example, a door that is opened and closed hundreds of times a day will wear down its battery on the door contact much more quickly than the same sensor on a window that is rarely opened.
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