Wow, I am getting into more preparedness stuff lately. I am trying to make sure that my family is prepared if something bad happens, natural disaster or otherwise. To this end, I am making sure that all of our cell phones have at least one extra battery full charged at all times. I found some good samsung mobile batteries online and I am working out a charging regimen.
Basically, I use a battery until it is on low batt and then charge it up, pull it out, and put in a backup battery. I repeat this every day so that I always have fully charged backup batteries no matter how much charge is left in battery in the phone at the time.