Architectural coatings are generally considered to be those coatings intended for on-site application to residential, commercial, or institutional buildings covering the amateur "do-it-yourself" and professional painters.
Their main function is protection but decoration also plays an important role.
Ageing of exterior coatings is very dependent on how well the original substrate was prepared and protected by the primer and of course due to light, heat (frost), moisture and oxygen. These agents not only work individually, but can be also combined to create a synergistic breakdown.
Decoration is their main function - protection is less important especially in the amateur "do-it-yourself" segment.
The frequency of repainting interior finishes is therefore mostly dependent on a need for a decoration change rather than to renew its protection role assuming that the original coating was applied correctly in the first place.
Ageing of interior coatings is more dependent on moisture affecting the coating as the natural elements cannot play a large role except to maybe fade the colour where the coatings are exposed to window light.