That’s a great question!
Wood Fence: Should last about 15 years. To keep the wood from rotting, apply a wood preservative to seal it. This is necessary for cedar fences. If you use pressure treated, a sealant isn’t necessary, as the wood has been injected with preservatives.
Ornamental Fence: Structurally will last a life time. After about 10 years, depending on the elements of the weather, you will need to have it sandblasted and powder coated again. If the rusting is minor, you can buy ornamental paint at your local hardware store for touch up.
Chain link fence: Fight rust with a rust- resistant finish. Check for loose screws and bolts. Oil the hinges on the gates to help keep your gate opening and closing properly