I have 45 Zigbee devices in my home, 33 of which are battery-powered. Those are door contact sensors, PIR motion sensors, climate sensors, and a few button remotes to control lighting. They're mostly from Sonoff and Aqara, with a few unbranded Aliexpress devices that identify themselves as TUYATEC, and a couple from Third Reality. In almost every case, the battery life has been extraordinarily good -- well over a year. The only exception is the Sonoff SNZB-04 contact sensor, which seems to need battery changes about every six months. Probably not coincidentally, it's the only sensor that uses CR2032 batteries, rather than AA or AAA. I would happily replace with a slightly larger sensor to get both longer battery life and less e-waste through the ability to use a standard rechargeable AA/AAA battery.