Hello: Letting a tank sit unused can create a smelly water situation. If that hasn’t been a problem, luck is on your side! 😉 An anode is the main ingredient in tank longevity. It’s affected by water conductivity and temperature mainly. Sediment is more of a concern in gas fired heaters as it gets in the way of heat transfer and causes tank overheating. If there is enough of it, the lower heating element will get buried, overheat and burn out.