We have several large storage tanks at our medical center designed to hold many thousands of gallons of diesel fuel for the generators for something on the order of 10 years. Generators are run once a months for 5 minutes and during a power outage. I would guess the tanks are topped off once a year. Whether or not the fuel goes sour depends on if you have a system designed for long term diesel storage or not. I have no idea what the Israeli Army uses.
All that fuel for that long and you never scrub it?