They don't specify a lifespan, but as LEDs it should be very long. Also, they appear to be designed to be driven at 12 volts, but the power supply they come with puts out 4.5 volts. The manufacturer says this is to create a more pleasant light (I believe them, and they have a glow of about the same intensity as standard xmas lights), but it should also mean that the lights will last even longer since they're being under-driven. I expect these to last a decade or two based on my experiences with LEDs. The part that will probably fail before the lights is the power supply, depending on how good the components are inside the little black box.