Sediment accumulation happens quite slowly, typically over several years. In electric water heater elements, this is found by an awful sculpture smell or by electrical component that was lower burnout. The lower part is the equipment that heats the water interior and is in the lower half. Sediment can pile up so high that the lower part is buried like an avalanche inside it. Hot water and your showers will come to an end in half the time if this occurs they used to.
It’s as much surface area and is almost as cold as a high-watt part. The heat that is lower heats the water in the same way quickly but creates much less sediment. If you replace a poor component, install a low-watt component in its position.