I remember the day a salesperson (known as tinmen and they actually made a movie about them) came into our house and sold my father aluminum siding and awnings. It was a pretty good move, the awnings would keep you dry when going in and out of your house during rain storms, and the aluminum siding protected the wooden areas of the house and garage, protecting them from the elements. However after about 25 years, even the aluminum begins to fade and dirt becomes embedded in the metal so much that it cannot be scrubbed out. Sure enough, another tinman came around and sold us some more aluminum siding so we should be good for another 25 years.
Edited: October 28th, 2006