How many hours of battery life does the Touch average with WIFI & Push turned on, but not actively surfing web? For work, I need to be constantly connected to our email Exchange server during the day. Office has wireless internet so I'm thinking about just connecting through wifi and using the Touch like a PDA. I don't want to buy an Iphone and have to pay for data plan / sign AT&T contract. Can the Touch battery handle a constant wifi connection and email push over long period of time? Just looking for a ballpark number so I have an idea what to expect. Also, do you think 3G will get a big bump in battery life?