High Heating Bills
The first step in this situation would be to have the heating boiler inspected for proper operation, the boiler could be running needlessly because of a malfunction which would waste fuel.
What type of heating system do you have?
On a hot water or steam heating system, replacing the radiator shut off valves in order to make them fully operational will only save money on fuel costs if you plan on shutting some of them off in rooms that are not used.