One question that is asked a lot online is how long does a set of batteries last in the Wii Fit balance board. I know because I was one of the people looking and mostly finding others asking, or answers that varied a lot.
I can say that I put in a set of Maplin home brand batteries (that are good value when they are on offer) and they have run for 20 hours already. The voltage has dropped a little so I don't know how much longer they have but I will keep going with them and find out.
Everyone else has reported a much lower time so I suspect that the board uses less power when no one is standing on it. This would explain why I am getting 2.5 times more use than anyone else.
Also it may or may not draw power when not in use. An old set of batteries went dead when the board was in the store that implies it does. Equally they could have been "borrowed" and put back flat. Currently I take the batteries out when not in use and that solves the problem for both potential causes.