Apologies Sideburns for the *snap*. It was raining here yesterday (whoohoo) and I drank a few extra cups of coffee. I was still probably suffering from the ill effects of triptophan. The combo made me a little on edge. No blood, no foul???
I didn't think the OP's question was ambiguous. To me, the question of "how the battery life is on the Nikon D80?? " refers to the life of the battery. I was told by an "expert" to figure that in 18-24 months of regular use, I could expect to start looking for a replacement.
I defer to those above with the amount of charge that you can expect on a battery. If I take more than ~50 shots on a given day, I will give the battery an overnight charge.