is more battery-dispendious shutting down or leave 3g on?
Turning off 3g and reactivate it later would consume less power, as all the data can be fetched once the 3g radio is in the high power state



When it is left idle, even for the most trivial data transfers, like checking the weather, the same cycle has to be repeated. Because of the long tail time that holds the device in a power mode, transmitting data as a series of small data bursts takes much longer and requires much more battery power than it does to send a single bigger burst.