Would depend what your shooting too.
Never used just one battery as i have grips for both of mine, but on 2 it last 2 whole days about 6hrs on per day in servo mode, plus i review every shot to check historgrams as i shoot in manual to check i am getting what i want in raw that used up 20gig in memory card space. I did delete quite a few too due to them being a tad samey or not being the angle i wanted blurred etc etc. Even then the battery's werent quite flat.