Available on Project MUSE and JSTOR. Online access to Contemporary Literature is available as part of the Project MUSE collections. All back issues of Contemporary Literature beginning with Vol. 1, 1960 are available online through the JSTOR digital archive.
Many manufacturers recommend water heater anode replacement every two to four years depending on the hardness of the water that passes through the tank and the quality of the water heater lining.
You can also make your old water heater last longer (sometimes 20-30 years) by replacing the anode every 3-5 years, if you have room to pull the old one out and install a new one. The anode corrodes instead of the steel tank, and when it's gone, the tank goes.