How long do you anticipate each set of coils to last? And how much will extra coils cost?

Our coils have been designed to last a very long time. However, they may wear out over time. The lifespan of a coil depends on how it is used. Bending or shaking will stress the coil, and may cause failure. Please check them before each use, using the coil tester provided. We will send you the coil tester for free.