The 'memo retention' at my company was about 30 years. We rarely needed anything past 10 years, but by that time people who were involved with a problem were retiring or dying off. If we did not have the paper record to defend ourselves with we would have nothing.

And when we needed it in court there was nothing like documents from the time to defend ourselves with. As our lawyers used to say, "It is not hard to find 12 people that hate oil companies."