What is a common issue that affects spares while they are on the shelf?

The most relevant issue that affects spare parts while they are on the shelf is corrosion due to moisture. When spare parts, especially metal components, are stored in environments with high humidity levels, moisture in the air can lead to rust and corrosion. This degradation can weaken the components, compromise their functionality, and ultimately lead to failures when they are needed.

While vibration, dust accumulation, and temperature extremes can also impact spare parts, they are generally less significant concerns in the context of parts that are simply stored on a shelf. Dust accumulation may require cleaning but typically does not cause immediate damage. Vibration can lead to issues during transport or operation but is not a primary concern for stationary parts. Temperature extremes can affect some materials but are not universally problematic unless they are extreme enough to cause damage, unlike moisture, which is a pervasive and constant threat in many storage environments.