I have my Thunderbolt brightness at 25%. which still sufficently shows the screen and it eats between 57 - 62% of the battery life of my phone. All other applications and whatnot were always under 9%. Yesterday I had my phone at 70% battery life with 4 hours of use. I say i used it on average. txting a lot. one phone call for like 3-4 minutes and playing words with friends and angry birds.