Both steel and reinforced concrete skyscrapers can last for centuries with proper maintenance. Here's a breakdown of their lifespans:

 Steel: Well-maintained steel structures can last for 100+ years. Steel is susceptible to corrosion, so regular inspections and repainting are crucial for longevity.

 Reinforced Concrete: Concrete is naturally corrosion-resistant, but the steel reinforcement inside can rust over time, causing cracks. With proper maintenance, reinforced concrete buildings can also last 100+ years.