A.O. Smith is not that well respected. Probably not the worst, but sure not the best. Most folks on this forum recommend the Bradford-White or the GE/Rheem. 7 years is not a very good life span for a water heater, but it could be minerals in your water that are to blame. By the way, builders are not noted for installing quality appliances. They go for cheap so they can keep the price of the home as low as possible and their profit margin up. We find that especially true with toilets. I don't know much about anode rods, but it seems that I've read that anodes rods rarely need replacing. That tank is usually shot before the anode rod. One other point about water heater warranties. The extended warranties are a con game. You get the same water heater and just pay extra for the extra warranty. When the tank goes bad, they prorate the warranty and it is usually almost worthless.