I suspect these batteries would benefit from calibration. Apple has recommended periodic calibration of the LiPo batteries in their laptops (charge to full, drain to empty, recharge to full). The LC-E4N charger can run a calibration cycle, and the 1D X tells you when one is needed.
I have had to recalibrate batteries for my 1D series cameras. I don't think there is a calibration for the 5D batteries