actual quality due to ageing
  1. Conceptual enhancements:
    Enhanced requirements, regulations and standards may result in an ageing of certificates.
  2. Technological enhancements:
    Technical advances / technological obsolescence have to be met. Enhanced test procedures or evaluation methodologies require a re-evaluation of some (old) analysis results.
  3. Physical ageing:
    Ageing of systems, structures and components (SSC) due to physical, chemical and biological effects,  resulting in degradation, corrosion, wear, etc.

The Ageing Management Process (PDCA cycle)