I have used the D70 (no longer have it) and currently use the D90 and D3100. I have two batteries for the D3100. Both of them seem to last for a very short time. I do not shoot video or raw (unfortunately).
On more than one occassion I noticed that the camera froze on me. Had to remove the battery and re-insert it. My main concern now is that when I leave the battery inside the camera, lets say for a week, I find it half empty. When I remove the batteries from the camera and re-insert when in use, it seems that the battery life if much longer.
This kind of battery power loss didn't affect my old D70 or my current D90. What do you think the problem is? Both batteries are Original Nikon Batteries (EN-EL14). Your help is most appreciated.