VERY FEW......
Most don't even KNOW that their water heater has an anode rod
Few that do know they have one don't think about replacement if they even remember
Most water heaters get replaced and they come with a new anode rod already installed
15 yrs and going strong.........
15 yrs is good service
Going strong----------that is debatable (heats water OK, hot water flows out OK BUT how much sediment and plating out has occurred lowering the capacity and recovery rate)
Besides anode rod....folks don't think about draining/flushing WH tanks at home either