Sounds like your charging is fine. Also sounds like there was a bad batch of X2s. I agree with suggestions about how you carry the Volts. I keep mine in a case so they won't get bent or knocked about accidentally. On the X2s - sorry to hear that. SI do have great customer service - it's one of their strong points. I'd say give it another go, but if you're still not satisfied after that maybe try some other KR808 stuff. And yes, QC issues seem to pop up across the board with minis and fatt batts. Some people have no problems with a product and others do. Some of the mods are problem free from what I've read here (I don't use a mod) - like the provari. I haven't heard any complaints. But it's big, and heavier, and battery safety with mods is very important. Not recommended to just put a mod battery in your pocket.
No, I'm not blaming the vender at all. As I've said, they're lovely, which is exactly why I'd hate to switch. If I changed brands I'd have to, though, as Certain V doesn't sell anything but Volt products.
And I'm pretty sure I'm not over-charging, either. Both the 78 and the X2 have a light that goes out as soon as charging is completed.