I've hunted for days with them. But, I don't use the tracking feature. I simply use it as a locator in 'Airplane' mode. Obviously, you have to get your maps right beforehand.
^ same here- 4-5 days in airplane mode with judicious use (and turning off at night)
I usually carry a Black Diamond Ember Light flashlight- it's a small 150 flashlight, but can also provide a full charge on your phone
http://blackdiamondequipment.com/en_US/headlamps-and-lanterns/ember-power-light-BD620801_cfg.html