Few things become less complicated over time. Lighting is no exception. More and more “other people” have something to say about the lighting you put in, and it is not enough to know the National Electrical Code (NEC) by chapter and verse.
In any lighting system, lamps and auxiliary electrical devices fail and must be replaced. Dirt and dust accumulates on fixture surfaces and should be cleaned. System problems must be corrected, and lighting controls should be adjusted as space conditions change.