New Iphone short battery life?

I just got a brand new iPhone 4S about I week ago… I absolutely love it… But the battery life is ridiculous. It lasts about 2 hours of continuous use and apple says it should last 8. The phone is brand new and has AT&T, if that makes a difference.

Charge the phone swotched of and then charge the phone fully again when the movile of on.

I have the same problem only got a new phone 4S 2 weeks ago and on standby overnight lost 50% charge.