100–200+ years. Copper roofs installed on European churches in the 1700s are still functioning today. It's the most durable roofing material available.
Yes. The patina (verdigris) is a natural oxide layer that protects the copper underneath from further corrosion. It's self-healing — scratches re-patinate.
For architectural statements, historic properties, and homeowners who want a permanent solution, copper is unmatched. The 100+ year lifespan means it's often the cheapest option when measured per year of service.