it's better if it is connected to a network, otherwise, it will keep searching and drain your battery. So, turn wifi on, only when you have a solid connection if you want to maximize battery life.
There is an addon called Addonis that automatically turns off your wifi when you lose connection. Haven't had the chance to actually see it turn off (since i just got my s2 about 3 hours ago) but if it does what it claims it should help quite a bit with forgetting to turn it off.
There is an addon called Addonis that automatically turns off your wifi when you lose connection. Haven't had the chance to actually see it turn off (since i just got my s2 about 3 hours ago) but if it does what it claims it should help quite a bit with forgetting to turn it off.