About Stand-by time (battery life)
Stand-by time (battery life) refers to the officially quoted time that a battery will last when the mobile phone is continually connected with the GSM network yet isn’t in active use.
The stand-by time is dependent on the phone network environment, for example, the distance to the nearest GSM cell tower (base station). Moving the telephone (as in a vehicle) negatively affect the battery life.
Phone manufacturers measure talk time in controlled conditions and the cited numbers are once in a while achieved in real life. These numbers are best used as reference when looking at telephones from a similar manufacturer since battery life estimation method will vary from one manufacturer to another manufacturer.