A well maintained water heater will reward you with a long lifespan, possibly up to twenty years.
By emptying out the water to clean the bottom of the tank, you will reduce a build-up sediment. Mineral deposits form at the bottom of the water heater tank and this greatly affects the efficiency of the heater.
To clean out the mineral deposits, open the drain valve and flush out the sediment through the drain.
Use several buckets of water until the water runs clear and there are no signs of sediment left.
By removing sediment and making sure that your water tank is free of mineral buildup, you can prevent serious damage from occurring to your water heater and increase the expected life span.