On a moderate usage, I got more than 12hrs of battery life everyday. ( I generally try to charge as soon as the battery falls below 40-50% ).
One day, I decided to try out the max. duration I could squeeze out of my phone. I charged fully and disconnect before I slept. These are the things my phone did that day.
-> Connected to WiFi for 7hrs.
-> Connected to HSDPA/3G for the rest of the time. (Most of the time, it was shifting between the two, trying to connect to the better signal)
-> Played Asphalt for about 15mins.
-> Used Aldiko Reader to read some book for about 30mins.
-> Facebook for about 30-45mins.
-> Voice calls for 45mins
-> Other misc. activities.
-> Only Gmail, Accuweather(3hr refresh) are connected all the time.
-> No auto-updates of any apps.
With the above things, the mobile ran for 22+hrs, after which it finally said "Battery Critically Low"

and did not show any percentage in the 'Settings-> About Phone-> Status-> Battery Level' option.