From what I can tell, areas of the luan have voids beneath the top
layer. Where these areas get exposed to water via a scratch in the
paint, the stuff gets saturated very easily. Areas where there are no
scratches in the paint seem to do ok. I abuse my boats but I expect
them to last. Anytime you beach your boat on an oyster bar you are
gonna get scratches. Having to apply a coat of paint more than once a
year is absurd.
In some areas, the voids seem to run in a linear pattern and then the
stuff is hopeless and the only solution is glass.