Can’t speak for thest of you folk but down here in the area my Comapny works in we have “Hard Water” and find that especially in gas fired water heaters that the life expectancy is around 8 to 10 years max. Those fitted with water softeners last approximately 10 to 15 years.
We have found on the hundreds that we have removed and replaced due to leakages that once the anode has corroded (been consumed) any flaw whatsoever on the enamel glass lining readily turns into a rust spot and from there a leak develops.
We have found that when transporting these water heaters many have had the anode break off and fall into the tank due to heavy and harsh handling – either from the delivery Companies or the Installers banging them about. This then leads to a very fast breakdown and the resulting leakage.
We have not yet (after 35 years of this kind of work) found one that had been used on a water softener to have failed earlier than one that has not been connected to one.
Tiss just a fact of life the manufacturers expect failures of glass lined cylinders and have down here at least given them a life expectancy of 10 to 15 years use in domestic dwellings with or without water softeners. 
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians
