I've lived in my unit about 5 years with a pre-installed Nest Learning Thermostat. I've only had to charge the unit about once a year until about 6 months ago when it started to need charge every 4-6 weeks. I have no wire C installed but do have Rc, Y1, G, W1.
Current device info: Battery 3.792V; Voc 36.4V Vin 34.33V Iin 40mA(i)
I have the latest software (just ran a check).
Sorry to hear about the trouble. I wanted to follow up and see if I could be of any help. Are you seeing any error codes on your device? There is a chance you may need to install a C wire/ Nest Power Connector. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.
There is a chance the batteries may not be holding a charge as well as they used to. You can resolve that issue by installing a C wire/ Nest Power Connector, as this will give constant power to the device.
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