Ford Courier heater element failure

hi there, has anyone heard of repetative heater element failures using genuine parts? My Ford Courier has just had the third heater fail in 8 months, is this something common to the breed or have I had the short end of the stick! The heaters have all been installed by a heater and ignition specialist who is just as puzzled as I am. This is all happening in Australia and I would appreciate any help you can give me to sort this problem out! :banghead: