You will get exactly the length of talk time on an iPhone that Apple marketing says you do provided you follow their simple 106 step guide* on how to configure the phone before you start testing.
*Note that this will render the phone largely useless for any other activity and you will need to reset your phone to experience normal functionality once testing has been completed.
*Note that this will render the phone largely useless for any other activity and you will need to reset your phone to experience normal functionality once testing has been completed.