How many hours of battery life can the Touch get with WIFI turned on all the time, but not actively surfing internet? I need to be constantly connected to my Exchange server at work during the day - since office has wireless internet, my thought is to buy a 3G Touch and connect to company email with wifi. I really want to avoid buying an Iphone and having to pay for a data plan / AT&T contract. I am worried that the Touch battery wont handle the constant wifi connection over long period of time. Do you think 3G version will see improved battery life?