I'll be able to give you a better estimate in a couple of weeks. I just replaced the battery in my iPhone 5 and the battery monitor is still recalibrating. Before the battery change, I'd see it dropping about 30% in an hour. But that's where the new battery comes in, once I hit about 40%, the battery would just crash down to almost zero very quickly. So, it will likely be better here after the recalibration takes. With the battery pack, I've gone 10 hours or more.

j.