Do you really think that a flashing LED is using THAT MUCH battery? Three AAA batteries in a nine LED flashlight will burn brightly for 10's of hours and dimmer for many many more. Your talking about a substantially less bright single LED flashing for a fraction of a second once every five seconds or so. How much more battery life are you really making for yourself and what good is it to have one of the most feature packed phones on the planet if you turn all the features off? I know a guy still using a old Motorola flip phone, only has to charge it once a week.
You would probably be better off reducing the polling frequency for email, lowering the screen brightness, etc. The flashing LED has got to be the most trivial drain on the battery in the entire phone.