Bush_walker wrote:its hard to see why you would want to carry the charger and an iPhone when you could be carrying a GPS with colour screen which is much more sturdy, longer battery life and has replaceable batteries. Then of course I would have a mobile with me anyway. GPS can't give me weather but where I walk there often isn't reception.
For me, the reason is that I'm reasonably competent at navigating with a map and compass, and have never owned a GPS, nor used one, until I got the iPhone last year. I certainly didn't buy the iPhone for its GPS, but since it has one in it already, and I need a phone, that's now one less device I need. So I don't plan to ever buy a stand-along GPS, when I really have no need for it.
I can use the iPhone while the batter lasts (more for curiosity and interest than for essential navigation), and revert to the map and compass for general navigation if I'm concerned about the battery life of the iPhone.
By the way, you can increase the battery life of the iPhone dramatically by disabling WiFi, Bluetooth and Cellular Networks. NB: Using "airplane mode" doesn't help, as this also disables the GPS (goodness knows why, as the GPS doesn't trasmit anything).
Disabling the cellular network is a bit tricky however, as there is no setting to do this apart from "airplane mode". I simply set a lock code on the SIM card, then when I wan't to disable cell phone network I just restart the iPhone, and when it prompts to unlock the SIM card, I hit "Cancel". Alternatively, you could just remove the SIM card altogether, but they're too easy to lose or break, I think.