Battery would die in 6 or 7 hours
It took me 3 hours to complete. I gave up 3 times and tried to find a place to take it for a new battery. All the repair shops said it was too old, no parts available, just get a newer iPhone.
The hardest part was re-connecting the tiny ribbon cable #3, almost microscopic and it took tiny tweezers to push it forward to eventually be pushed in place by the mother board as it went into place from behind and over it.
The rest of the instructions were clear enough to follow.
It would be helpful to have a better video with closer views of the connectors and how they go back together. Taking it apart is covered well. Just stating "repeat steps in reverse" is sort of a joke. When it comes apart, you can't tell how the cables are fastened. You can't tell how some of the cables go back in at all. Some snap down, those are easy. #3 slides in from behind, sort of. A video of how it is done would probably really help.
The repair kit was imperative to changing the battery out, glad I got that.