I've got one of the prematurely dead eGos. I used it for about three weeks, rotating it with the other battery that came in the set, with even less use when I tossed a RiVa into the rotation. It died, went onto the charger (USB/AC adapter one) okay, did it's thing (light started out red, eventually turned green), took it off and it worked an hour. Didn't even think about it at the time (thought it was the other battery until I realized what flavor had been in it). Screwed it back into the charger....the LED started blinking until I unscrewed it. Screwed it back in, the light on the charger is green, nothing on the battery. Then I tried just using the USB fast charger via the laptop, battery light blinks about 2/3 through screwing it on while the charger light stays green. If I leave it in that position, it just continued to periodically blink for a while as the charger button still does not change, although even that quit after about five minutes. I tried it on my RiVa USB charger at that point and it did the same thing.
I'm afraid to plug my other eGo battery in for fear of what it might do. I've got a 510 charger somewhere around here, so when it dies, I may try that and let it do a slow overnight charge. I've relegated it to using my 2-hits/day flavor just to prolong it's life as long as I can.