Why aging Great Lakes freighters need replacement

How soon should the aging Great Lakes freighter fleet begin to be replaced?

As soon as possible, given the age of the ships and the much older design assumptions behind many of them.

The question identifies a fleet largely built from the 1950s to the 1970s using much older design traditions. The recommendation is to begin replacement as soon as possible. The emphatic judgment draws on one participant's experience making television programmes about lake freighters lost in storms.