How long will an oil tank buried in the ground last?

I have seen tanks fail in 10 years and, also, tanks that do not leak at 50 years of service. Many factors contribute to the life of an underground storage tank,
some of these are:

thickness of the original tank water table soil acidity stray electrical currents age of tank

Many tanks were installed post WWII when a lot of new homes were built and are now at the age of 50 years +. Dating a tank by the age of the house is very common because tank replacement generally only happens when there is a problem with the existing tank. Older homes were probably converted to oil from coal or wood around the 1940's.