galvanized metal roofing, durability?

[Durian Fiend]

Aluminum doesn't rust.

I've never seen an aluminum roof.  What's the price comparison? Here's a longevity comparison of metal roof options for Hawaii I found online:

• Galvanized steel is known to have a lifespan of 25-30 years,
  
  
• Aluminum roofing can last up to 50 years.
  
  
• Copper roofs can last for more than 75 years, making it one of the longest-lasting roofing materials.
  
  
  

My steel roof from HPM is currently 30 years old and not in need of replacing.