20 - 30 minutos
phone is just two years old. It started to shut down and reboot randomly...problem progressed until it would only stay on for 3 minutes before rebooting...then progressed more until it would only come on if connected to power source, but it wouldn't connect to any data networks.
I got a tip that it may be the battery. Ordered it, came a day earlier than expected. Install was easy following directions found here. Phone is back to 'normal'.
I still had intermittent functioning problems...I did a restore with a fresh version of the ios...4.3.5 I think...and no more problems.