Well, part of the problem is the weak resistors that are built into the light itself and another problem is the contact wire of the bulb on the same side as the resistor is a lot smaller and tends to heat up with the constant flow of current. There's not really a cost effective remedy to solve your problem. You're just going to have to keep trying different ones until you get lucky. Lol
Here's a link to the last set I bought. These may have more SMD's then the set you bought but that might help reduce the chance of failure. These are also a little more expensive.
These are a little cheaper but that's because they'll ship out of China and it'll take about a month to get here.http://pages.ebay.com/link/?nav=item...obalID=EBAY-US