Galvanized steel metal roofs are a wonderful invention. They can easily last 60 years or more but do require upkeep. Aluminum roofing is much less upkeep intensive and naturally resistant to corrosion. Aluminum can last 30 years or more. If you really want a lifetime roof, consider copper. Extremely expensive and difficult to obtain, copper roofs have been known to last hundreds of years. One of the issues with metal roofs is that they can be damaged by walking on them and can be dented by falling limbs or hail stones.