Something wonderful has happened to my Galaxy S3, it actually stopped using the battery when the display is off and all connections are disabled. So far with 5 hours of music playing, 2 hours of on screen time and 45 minutes of surfing the internet via WLAN and 3d it has lasted 5 days and 12 hours and still has 13% remaining.
In the previous year I've had it, the longest it lasted (with similar usage mind you) was 4 days. I don't know what happened or why, I didn't change anything, but at least for this one glorious recharging cycle I'm actually happy with the battery.
I only dread the next time I charge it's going to go back to its old ways :/