I am often asked how often electrical systems should be inspected. Traditionally, most people would undertake an annual inspection of electrical systems, and perhaps semi annual or quarterly inspections for mechanical systems.

NFPA 70B recommends:
"Routine infrared inspections of energized electrical systems should be performed annually prior to shutdown. More frequent inspections, for example, quarterly or semiannually, should be performed where warranted by loss experience, installation of new electrical equipment, or changes in environmental, operational, or load conditions."