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What is the typical user experience with regard to ZSE42 XS battery life?
My first couple of batteries didn’t last long at all: maybe a month or so each. Before replacing the battery the third time, I installed a ZEN76 v2.0 700 Series S2 On/Off Switch nearby to control the basement lights and (likely) provide a better Z-Wave signal for the ZSE42 XS (the SmartThings hub is one floor above and I only had one other old Z-Wave device in the basement at the time, perhaps even farther as the crow flies from the hub). Since the latest battery was installed last October–resetting & rejoining the water leak sensor to the hub in the process–the battery is at 43% after approximately six months.
At that time, I also set the LED indicator to ‘Disabled’ (you can’t see it when the cover is on the device anyway!) and wondered if that has any bearing on battery life?
The LED Indicator setting (parameter 1) would only affect what the LED does when the sensor detects water. Unless you’re always detecting water I don’t think it would affect battery life. My experience with both versions of this leak sensor (old one used CR2032, new uses CR2450) is that the battery lasts around a year. The new version might be a little less. I’m using it with the Zooz hub. Other devices are relatively near all my sensors, within 30 feet for sure.
The polling or wakeup interval can be a problem for battery devices. The Zooz hub default for that on this sensor is 43200s (12 hours). I’m not sure it needs to be even that frequent but I’m okay with the battery life so I’m leaving it.
I’ve also found that off-brand button batteries can be much more variable in their longevity, sometimes even showing up at less than 100% when I first install them. I’ve had good luck with Energizer lately and good deals can sometimes be found on Amazon for those.
ZSE42 FAQ: the best place to start 
What’s the Difference Between the ZSE42 (700 Series) and the ZSE42 800LR (800 Series)
OTA Firmware Update Files: read all of the disclaimers carefully before applying an update to your device to avoid accidental bricking 
ZSE42 Change Log: where we keep track of all the updates made to the hardware and software of the device.
ZSE42 Specs: make sure you use the device with the right power source and keep it under acceptable conditions.
ZSE42 Advanced Settings: learn how to customize your device.
Detailed Support for ZSE42 XS Water Leak Sensor & Your Hub: