The issue with batteries... strange how it's been so difficult to get answers about the simplest of things! From the start we've wondered how to properly store batteries. Of course we know how to store LiPo batteries, but Solo's Smart batteries are a class unto themselves.
It seems pretty simple to me, though. I've got 8 batteries and they behave identically - apparently they stay "awake" for awhile after being charged or used a little, then go to sleep. Kind of like a computer.
Try it yourself - charge one, then leave it alone for a day. When you then press the power button to see the charge level you'll notice it takes two presses of the button. One is obviously to wake it up.
Whatever the case, if you charge it then leave it be for a couple of weeks, it'll be at roughly 50%.
Yep, that's not scientific and your mileage may vary, but I don't worry about my batteries any more. Charge 'em and forget 'em. They'll drop that far and no further.