Regular cleaning of surfaces will dramatically extend the life of the coating. This is true indoors and outdoors. The build up of dirt and salt will attract moisture. For most indoor cleaning use 100% Terry Cloth Rags for cleaning. They are inexpensive, absorbent and just rough enough to clean most painted surfaces really well. For outdoors rags can be used as well on smaller items like a basic door surround. But for larger expanses of siding, walkways, eaves, soffits and facades I would recommend using a stiff bristle brush on a pole in conjunction with a good hose, or power washer along with the right cleaning agent for the task.