Do you switch your phone off at night? I make a point of doing so. It saves on power since you are not likely to use the phone much at night unless you are a night bird, for example night shift workers and sentries. I have also noted that this prolongs battery longevity which spares one the cost of having to replace them. I have a Lithium ion battery and have used it for more than a year now with no sign of depletion.