The all important question -"how long will my fence last?"
Oak and chestnut are incredible durable and can last up to 20 years with ground contact. Most untreated fencing has a life of 5 years with ground contact. Soil conditions and drainage will affect this though. All our fencing however is pressure treated extending this life to 5-10 years on average at ground contact. Above ground though softwood fencing will last a lot longer. One of the main failures of fencing is post base rot. This is why we often recommend a repair rather than a replacement.
So it's a combination of installation, quality of materials, weather, ground type. Of course some fences get vandalized especially when facing public areas. For this type of fencing we recommend extra strong closeboard on strong cant rails.
Steel posts last longer than concrete and timber and are recommended.