20 - 30 minutos
Battery on my old iPhone 3GS started losing its charge too rapidly to count on it to last half a day without charging it either in the car or at my desk at work.
The repair went pretty much just like the instructions said it would. Unfortunately, the glue on my old battery was strong enough to break one of the ends off the tool that was included in the kit. Thankfully, that tool has two usable ends.
I used a small suction cup to lift the screen from the case. I felt safer doing it this way. Be very careful with the little clip holding down the camera. The screw that holds it down tried flying away on me when I wasn't as careful as I should have been pulling the camera up and out of the way.