Nearly all elements and assemblies in a typical American house built before 1940 are meant to be in service for the lifetime of the building. With proper maintenance and repair, those elements can last for several generations as they were built. Even without that maintenance and repair, those elements will serve their intended purpose and fail very slowly, giving any owner ample opportunity to perform repairs that return them to full function. Once the system has endured extensive decline, restoration can be performed and failed parts can be remade and installed into the remaining original. Window systems should always be made with components that can be repaired or replaced instead of having to remove the entire assembly to be replaced by a totally new one.