20 - 30 minutes
My iPhone 3GS, at something over 3 years old had reached the point where it would operate for only 5 or 10 minutes, even after being fully charged.
After too much frustration, and not wanting to spend a lot of money to have it repaired, I came across one of your videos on YouTube.
Ordered the repair kit. It arrived as scheduled and I fixed it that same day.
All went well, thanks to the step by step repair guide on your site. Took it slowly and carefully so it took me about 45 minutes to complete. The phone is working just fine now.
The only advice I'd have is to simply follow the repair guide and don't rush. No problem.