Depends on the resolution you record at. On mine it has ultra fine ( use if have an HD tv ), fine ( the one I usually use ), normal and economy.
Ultra fine gives about 7 hrs, Fine about 10.5 hours, Normal about 14 hours, Economy about 37 hours. With each of these you can also insert a SD card which gives additional space. For a 4 GB - Ultral 1 hour, Fine 1.5, normal 2, Economy 5.
Of course before all you space is used up, yo can upload what you did to the computer and then delete what you used. These are all record time though, not battery time
Very helpful, TheCipher. You guys are making the job easier.