I've been thinking that structures that are used like Kilns and ore smelters should break. When I say break I mean that they need to be repaired not destroyed. When you right click on the broken structure a menu could pop up showing what materials you need to fix it. It could break after a set time period and number of uses. The materials could also be randomly chosen from the materials used to make it.
I thought this would help make sure that materials are always needed and help in creating a constant trade system.
*not sure if this is already in game I haven't encountered it yet*