...are mothers and cell phones... you are not going to break it, and running out of battery isn't going to hurt anybody... JUST LEAVE THE DAMN THING ON.  The point of a cell phone is to use it, and allow people to reach you no matter where you are. 
Both my mother and Sherry's mother are cool enough to have cell phones, yet... neither one of them can EVER be reached by it.  What's the point?!!?
Sorry... just had to vent.