Is it totally wireless or just wireless to the derailers? How much freaking battery would be needed to transmit switch commands from the shifters to the derailers anyway? Look at a wireless bike computer, that wireless sensor is basically telling the head unit...yes...yes...yes....how many times in a minute? So pushing a button on a shifter isn't going to take up that much juice to transmit.

A watch battery in my V3 lasted for 1 year in my V3 and it was 2.4 ghz and coded. One each for the shifters. One for the derailers to pickup the command and another battery to shift.

wireless to the derailers just means the same battery as before with a battery to receive the codes from the shifters.