Our 18 Gauge Wire is Heavy-Duty Wire, and the insulation is PVC just like soda bottles that don"t disintegrate in land fills. Assuming you bury the wire deep enough so the lawn mowers can"t get to it, our wire will last for decades! Why you would want the heavier 18 gauge wiring: 1) Your soil type is a rocky or harder type of soil, making it difficult to securely hide, or bury the wire at least 6" below the surface; 2) Your yard has active, fast growing trees, bushes, or any type of aggressive vegetation that could eventually cause snags or breaks, exposing the wire; 3) If you are planning to install the wiring on or above ground; 4) If the installation of the wiring will cause it to be near high traffic areas, where animals, people, or vehicles will be crossing over the wire, even if it is buried, or concealed.