I am hesitant to brag as I bought the cheapest strings of led lights I could find. After reading how the cheap ones won't handle higher voltages I made the decision to install a dropping resister on the input to each light.
I did this over four years ago using 4 strips of 12V 5M 500CM Waterproof Warm-White 5050 300 LED's in each of my fixtures. I stripped out the ballasts and just used the shells.
I was worried about the led's burning out as the higher the voltage the more current they draw (LED's work backwards from everything else electrical) . My solution was to take the highest voltage I thought they would see calculate the current draw for the four strips I was using and then buy dropping resistors to make sure the led's never see over 12 volts.
So far I have not lost one LED and I really don't notice any dimming of the lights when my batteries start to get low.
A lot cheaper than buying expensive LED's or installing regulators and much easier to wire in, just have to make sure the resistor is placed where the heat can dissipate.