Awesome tips. I'll try increasing the refresh interval to 2 minutes and turning off the wifi in between refreshes to see if helps with battery life.
Side note this also finally explains to me why battery life on the Kindle is SO good in airplane mode.
Could you adjust the refresh frequency based on your usage patterns? So refreshing less frequently outside your main transit times. An extension of your current pause at night.
Yeah you'll probably want to turn on airplane mode between the refreshes. That's at least what KUAL "Online screensaver extension" from Mobiread forums does, with it I'm getting several weeks of battery life with refreshes every couple of hours.