Hi Dan,
When i bought the passthroughs from MadVapes, I read the reviews. One person said to reinforce both ends of the wire with electrical tape. I did that and mine has been working for 2 months! I even mash the thing putting it in my purse!
At the USB end that I plug into the wall adapter, I taped it rigid into a line so that it couldn't wiggle any way- it's immobile. At the other end of the wire that goes into the LED light, I formed that wire into a loop and taped it 1/4 inch away from the LED light. It's tape4d to the body of the passthrough but I can still see the LED-light light up and the tape doesn't interfere with the button. That wire can't wiggle either because it's taped into a very short loop.
From what the reviewers were saying, it's the wiggling motion of the cord that makes them short lived. Try taping your next new one and see if it prolongs it's life. Get the wall adapter too for $10. No sense taking a chance of frying your motherboard!
Lori