Because electric guitars are high-impedance devices, this means that their tone is affected if carried over long distances. Impedance means that the longer the signal path, the more noise, and resistance occurs along the way. After intense testing, it has been concluded that around 18.5 feet there is the maximum length of a usual instrument cable where you can still clearly hear and easily measure the sound changes in a guitar’s tone.
Furthermore, passive pickups give out a higher impedance output, and that means they will be more susceptible to tone degradation on long distances, compared to battery-powered preamp pickups. Given that most guitars have a passive pickup, you will surely have a high-impedance instrument on your hand.
If you are not using a cable made with oxygen-free copper or linear-crystal copper, it would be a good idea to keep the cable as short as possible.