Depends on Activities you do
Minimal Activity I can go about two days without needing a charge.
Listening to MP3 almost all a day or about 12 hours, sending and receiving txt, etc..(drain's about to 50%),
Heavy Usage - Gaming, Video, streaming over Cell and Wifi can drain the battery pretty fast in about 8 or so.
I have had good battery life but it all depends on what you using your phone for has well..
My Input on Flash Battery Life