If the firmware update changes the power characteristics of the device, it would probably be a good idea to let the battery drain totally through usage to calibrate the battery meter - if you're bothered about using the meter.
I keep my battery fully charged by connecting the Gen3 to my PC for a few minutes every day, so my battery meter generally stays on "100%". I'm sure it would be horribly inaccurate if I were to let it drain more!
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