There is no easy answer. It seems different engineers have different
practices or policies. I must agree with Roger that saving design documents
is more appropriate than discarding them. Also, I agree with Dennis, that you
cannot be liable for over design however you will lose clients if they
believe the "engineer down the street" can design for less money. ( Now I
wonder who his insurance carrier and lawyer are?)
In New York, I was told, " If you sign and seal a document, then you are
responsible for it, forever" however long that may be. That's why I save all
my documents.( One reason I have a Basement).
John G., P.E.