While Li ion batteries tolerate cold temperatures better than some other types, they still drain much more quickly in freezing temperatures. If you are leaving your Flyer in screen-off mode (and not powering it down), then you should be careful its not draining until shutoff in cold temps. Full power cycles are not good for Li ion batteries long term. Its also possible that draining the battery until the device shuts off, will render the battery unable to take a charge. (doesn't happen often, but does happen with Android devices).
That said, I completely understand your feeling about wanting to use an Android device instead of a Garmin for car navigation. I haven't used the "latest" Garmins. But the one I have (couple years old) has a crappy unresponsive touch screen, low resolution, and search function is nothing compared to Google.
The only advantage to a Garmin, is that you don't need a data connection. But of course, there are ways around that with Android also, either downloading Google Map sections, or with 3rd party software.
Please click the "Thanks" button if you found a post helpful!
Phone: HTC One X (AT&T version) Rooted, Bootloader Unlocked, S-Off
Tablet: Samsung Galaxy Note 8 (WiFi only) Rooted