so the moment I power down my phone to save battery and start it back up, all the cached pages are gone
Sad but true.
Also, if you power down and are not in cell range then you cannot start Gmap4. You can only start Gmap4 when your browser is online.
If you are on a day hike then one option might be to leave your phone on but your GPS off. (GPS is a battery hog) Only turn the GPS on when you need to check position.
