Sony have put up specifications for the PlayStation Vita, including details of the device’s battery life. From the spec sheet, battery life is detailed as follows:
Game: Approx. 3~5 hours
Video: Approx. 5 hours
Music (in stand-by mode): Approx. 9 hours
A note adds that the 3~5 hours is if you’re playing with Wi-Fi and Bluetooth turned off, with the screen brightness at the default setting, and with headphones on. Additionally, they also mention that charging the battery from zero to full will take approximately 2 hours and 40 minutes.