One of the primary predators on electronic equipment is airborne dust. You should cover your mixer, exposed gear, and keyboards when they are not in use. Dust build-up will cause mixer sliders to become noisy, and can cause synthesizer keys to trigger inconsistently or stop playing completely. It’s not just keyboards and mixers that are targets for dust, almost any type of gear will suffer if exposed to dust for long periods of time. A variety of stock and custom-fitted equipment covers are available for very reasonable prices — cheap insurance!