15 minutes - 1 hour
My battery on my Iphone 5 would constantly die, it would go from 100- 70% within an hour and then it would die almost instantly when it would reach 55%.
The hardest part was taking the battery out of the phone. It is really glued in there. With alot of patience it will come out. The new battery is working great. My phone lasts the whole day without needing to be constantly recharged.
I wouldnt say that this is the easiest of repairs due to the tight space and the strong glue used by apple. As long as you take your time you will be able to do the repair.