It depends on exactly what symptoms you're getting. If you're experiencing poor heating in either of the Economy driving modes, that may be because the highest level of heating is reduced with those settings.
But if you get intermittent heating in Comfort mode, the heater element is probably on its way out. You should be able to get more information from the car's diagnostic data, as I believe an open circuit on one of the heater circuits should generate a fault code. They are not (in my part of the world) cheap to replace.
