Having worked in a smartphone after market organisation, I can assure you that phones do break due to user error also in the first few years. Screen breaks, phones are dropped, charging ports are subject to user violence… while this is apparenrly not true for you, there are probably hundreds of thousand of fairphone users, so I think their spare parts availability is really good. And as I said, even now you can buy spare parts for discontinued fairphone models from ebay and other 3rd parties.