I am a homeowner in Maryland, grateful for your informative website.
Kenmore, Whirlpool, and Rheem (GE) are the only manufacturers that offer the 9 & 12 year warranties. This seems to have more to do with the Retailer than it does the manufacturer. We have seen ZERO correlation with 12 year tanks and longer tank life. Here is the data we are basing this off of.
Rheem Water Heaters
Whirlpool Water Heaters
Kenmore Water Heaters
Manufacturers have to replace water heaters under warranty from time to time but it’s usually related to thermal expansion or high water pressure. They do a great job of making their tanks to last even under extreme conditions. Contrary to many people’s belief, they do not design their tanks to fail a year after the warranty expires. They design them to withstand extreme conditions for as long as possible.
If you want your water heater to last check your water pressure. Open loop systems are always better and will have longer tank life but if your water pressure is over 80 psi you will have to install a PRV.