The initial function and performance of the paint film decrease due to deterioration factors such as ultraviolet rays, water, and exhaust gas.
There are usually various stages of deterioration.

1st stage: Appearance performance is lost due to dirt, discolouration, etc.

2nd stage: Surface deterioration of the paint film progresses causing chalking, abrasion, cracking, etc.

3rd stage: Cracks in the paint film progress to the substrate. Lifting and peeling begin to occur.

4th stage: The continuity of the coating film is lost. The adhesion to the substrate and the protective function are lost.

Among these, the 1st stage is too early to repair because the protective function of the paint film has not yet been lost. Since the time to reach the 2nd and 3rd stages is the best time for repair, the period until reaching these stages is the lifespan.
For the 4th stage, the durability of the paint film cannot be expected. Therefore, the existing paint film should be completely removed and repainted with a new coating material.
Deterioration is usually complicated by various factors such as materials, regional characteristics, the application level, maintenance, parts to be applied, etc. Considering these points, we have set the expected lifespan.