After the protective patina forms, corrosion drops to little more than a few millionths of an inch per year. The point is that copper lasts a long time, and most of what has been used before is still around, being used again in another form. Copper that is no longer useable, such as old wiring and plumbing tube from demolished or renovated buildings, is collected by companies that make up the very efficient recycling industry. We used to call them scrap dealers, but they're really a key part of the nation's recycling system. They sort the old copper, bundle it and otherwise prepare it for market.
Refineries buy the recycled metal and convert it back to pure copper.
As an important added benefit, re-refined copper's lower energy needs mean less fuel consumption and fewer emissions of unwanted gases to the atmosphere. No question, recycling copper is a win-win situation. A lot of recycled copper scrap is bought directly by mills that produce roofing sheet. All rely heavily on scrap copper as one of their raw materials. Some of these companies have the capability to re-refine scrap copper to the extent needed to make new roofing sheet.