That depends on several factors as listed below:
1) Amount of minerals in the water, for the most part Citrus Heights has good water, meaning a moderate amount of mineral content (ppm) are present.
2) Flushing the tank once every 6 months when minerals start to collect in the bottom of your water heater tank, it's first actually like in a jelly form, before they solidifies (harden), this is when you want to flush your water heater tank (under pressure), do NOT drain the tank with the water inlet valve off.
3) Change the anode rod, the anode rod should be replaced when it is 50% spent, or at the least every 3 to 4 years.
If the above maintanence is done on a regular schedule, your heater should last an incredible 15 to 25 years, if not, it will only last 9 to 12 years on the average in Citrus Heights, California and most areas of Sacramento county.