I tend to try and wait for my battery to drain completely before fully charging it back up to 100%. I happened to drain it completely the other day and put it on the charger and it was fully charged before going to bed. I woke up the next morning and the phone was at like 95% after being off the charger all night. I went to my college in the morning at around 6am to study for a test coming up later that morning. By 9am I look at my phone and the battery is down to 60%. I was blown away because I had not even been using my phone. I then realized, my school makes you log in to the wifi service in order to stay connected to it, but I had previously connected to it before with my phone so it was in the phones memory and my iPhone 4s spent the entire 3 hours trying to connect over and over again to the wifi. This burned through my battery very quickly. There is no option to have your wifi service only connect on choice to previously remembered wifi. There is only notification option of available wifi which will ask you prior to connecting to new wifi options. The only other option is to turn off your wifi all together. So keep in mind that if you have a wifi source that you have previously used for your phone and you might be on the border of where that service is available, your phone might be disconnecting and reconnecting to the wifi. This can cause significant battery drain.