It is recommended to flush your water heater at least once a year and replace anode rod(s) every 3-5 years (or less). If you wait until your tank ruptures, you could end up with a flooded home.
At a minimum, a water heater should be inspected and flushed every 12 months. For well systems, you can cut this time in half.
No water heater will last forever. Are you experiencing any of the following signs?