Yeah I find it can last me little under a week or so if I don't use the phone for anything but photos. Plus it isn't hard to find an hour or so somewhere where someone can let you charge it up.
Add to that the risk of theft, them breaking, the fact that i'd have to carry another light anyway as a torch, and the cost of the lights, and the benefits for me seem less and less.
Unless you're going to be riding through the night, a headtorch is usually bright enough, you can get them with AAA batteries.
Choose device that can accept the universal micro usb port, if you have an iPhone for instance, you can get those Apple Lighting to micro usb adapter which is tiny.
Yeah I find it can last me little under a week or so if I don't use the phone for anything but photos. Plus it isn't hard to find an hour or so somewhere where someone can let you charge it up.
Add to that the risk of theft, them breaking, the fact that i'd have to carry another light anyway as a torch, and the cost of the lights, and the benefits for me seem less and less.
I'll probably just stick with the standard XT