I have about 20 lights, with varying voltages between 12 and 14V, and I think I've gone through about 12 of these in a year. I don't think its the voltage, however, because I have about the same failure rate on each circuit. The only good thing is these are dirt cheap. The original bulbs that came with the lights went out just as often, so I can't say that these are any better/worse than those. Not sure if they were high quality to start with. Again, just buy a bunch to have on hand.  Gotta go change 2 now.