I don't bother myself given the cost vs benefit vs my time, but I've come round to being convinced that storing somewhere below maximum capacity is probably a good idea as there could be some chemical unpleasantness if you leave a lithium cell fully charged.
However, I'm not even sure what we're looking at in terms of voltage, given that a typical charger will pump cells to 4.2V rather than the nominal 3.7V, and that voltage and capacity aren't a linear relationship. 70-80% of maximum charge would mean a cell voltage of something like 3.95 - 4.02V, but I doubt that's what a charger will set as a storage voltage (and it can only see the voltage and resistance, not the actual charge).
I'll storage charge a 2S on my B6 and see what it settles down at. I've never done this before, I reckon I'll see something like 3.8V per cell / 7.6V, which would only be about 40% charge, but I'm all tingly to find out (or that could be bad earthing).
[UPDATE]
Yup, 3.8V per cell, or about 40% charge. I'm surprised it's that low, I used a lipo that hasn't been charged for many months, and it still had to discharge it down from 4.0V per cell.
