I've been buying the 9 year water heaters lately from Home Depot and have been thinking about purchasing the 12 year heaters from now on but is there really that much of a difference between a 6 year and a 12 year other than the warranty? I've heard they use 2 anodes in a 12 year. Is it really worth the extra money, sometimes over $200-250 more than the 6 year tank? I plan on flushing all my heaters once in the spring and once in the fall every year and replacing the anodes every 3 years or so. I've done some research and found many people say the 9 and 12 year tanks are just a rip off. I want to buy the best product for the value. What do you put into your properties and generally with proper maintenance, how long are they lasting? 

I see alot of 12-18 year old tanks in the properties I purchase and aside from being limed up, they function. I just replace them with a new one to save hassles later.