I had my first one die recently, got it in February.  The last week or so before it passed on, it wasn't holding as much of a charge.  Where as before it would last longer than I could vape it in a day, it started dying at 8 pm, then 6 pm, then 4 pm, then it didn't have a charge at all.  I plugged it into the charger, and the button would blink, but the charger didn't change colors.  I'd take it off, press the button, nothing, no lights, no vape.  It was 1 of 2 I got in the kit, the other one still being practically new since I always just used the other one.  I have 2 650s in reserve as well, so I should be good for awhile.  Not sure if that info helps at all.