To keep track of my pace. I take my iPhone along when I go running. Lately, it has gotten colder (30F to 45F) and it seems like my battery appears to die quickly. Sometimes I've taken it biking (when I don't time myself) and found it turned itself off when I return home (yet I can still turn it on after it warms up). I've had an iPhone 3, 4, and 5 and I've never noticed this on any of my other phones. Does anyone know if the battery in the iPhone 5 is any different than the previous models (more temperature sensitive)? Is my battery nearing the end of its life prematurely?