Each mechanically driven clock is unique. All clocks, without exception, have parts that wear because there is metal on metal contact, which results in wear and tear. This wear has to be addressed by replacing parts or by repairing parts. This is no different to anything mechanical such as an appliance in the home or indeed a car. The cost of repair is related to the amount of wear. If a clock has been left untouched for many years, then the wear will be accordingly that much more.