I have just started using a couple of sleep aid apps....White Noise and Sleep Pillow. To run 8 hours at night they use about 30% of the battery power. To avoid this battery drain I could just plug in my iPhone and then run the app for those 8 hours. In the long run is this likely to negatively impact battery life more than the increased frequency of charging that I am faced with if I don't plug in the iPhone at night to run these apps?