I think my MV batteries didn't last because they constantly needed to be adjusted. They lasted about 3 months or so and both died within a couple weeks of each other. Even so, you figure each battery cost me about $5 a month so I'm not complaining really.
Yeah they must have had a batch with a out of tolerance connector (my guess is too tall)..they had a bunch of them in the bargain bin..that's the smok Tech 900mAh eGo's I have I paid $9.99 each for them..are those the ones you had that failed?
It was posted to file them down 0.5mm or pull the pins up..I filed 2 of them and left the 3rd..all 3 I have to pull the pin up slightly on occasion but not one has failed yet..I kind of wish one would so I can have an excuse to tear it apart and see how it "ticks" lmao..I like taking things apart I have been taking things apart since I was a small child and I can usually put them back together...