At -50mV across all frequencies, it reeeally varies. I never have a "normal" day with this phone. But, the shortest I've had using Ziggy's kernel from 192-1836gHz with on demand governor is around 7 hours. That was pretty heavy usage for me. Some games like Dead Space and Captain America, tons of internet, Pulse, texting, a few phone calls, music, and a little Netflix at night. The longest I've had has been 20+ hours. That's with very little gaming, a little internet, and mostly just texting. Stock battery, bump charged.
I'm really afraid to go too low, though. One time I was just seeing what would happen if I kept lowering it across all of the frequencies and it froze, then crashed. Had to battery pull to get it to work again.