A picture is worth many words, if I didn't see this photo I would have thought it's a joke, but now I think you're a dealer...
I wrote a short review on my blog recently on caring for lithium-ion batteries, involving the practice of keeping a battery partially charged when not in use, but when your collection gets this big...
I too follow the rule of swapping batteries frequently, on my DeWALT DCS570 I swap the 5AH battery as soon as it reaches 2 bars when the situation allows, this way it functions at full speed and is good for the battery as I'm only shallow cycling it rather than using all of its juice up.