I think you are over rating the accuracy of the battery readings. I'm not sure these numbers are absolutely real. I think they are just approximation of how much power is left. The only way to really check how many shots your battery will take is to take pictures and run it down.
I wonder why this seems so important to you... I never ran out of a battery while shooting in a day. If you want to be on the safe side, carry an extra battery with you. Otherwise, I think you're just trying to be a little to fussy about it. If you spend your time looking at how much power is left in the battery, you might miss a great shot...
I do realize that the 900-shot battery life claimed by Nikon could be over estimating it. BUT, most people that I know that use a D610 get 800-900+ shots from each battery charge.
My problem was that my camera lost battery life just sitting in the bag while TURNED OFF, overnight. 3 percent of my battery went *PFFT* into the ether while nothing was running. That shouldn't happen. I had used my camera for a few days after I got it, and only managed to get 225 shots on a complete charge. 225 shots is nowhere near a good number. *THAT* is why I'm concerned and running the tests suggested by Nikon and B&H.
I have spare batteries that I can carry, sure. But if I'm only going to get 225(ish) shots from these batteries that should get WAY more, then I'd have to carry a pocket load of batteries every where I went, and that doesn't work for me. It's obvious that something is wrong in either the charger, the batteries, or the camera. But, because I'm using 1 Nikon battery, and one Watson battery and BOTH are discharging rapidly, it's looking like the camera itself is discharging the batteries for no reason.
I just spent $2400 on new gear, so I'm *going* to be a LITTLE picky at first, but only because I KNOW that the equipment *should* be getting better battery longevity than that, and it should not discharge my battery so quickly if everything is turned off.
