And? A better, corrosion resistant material may last indefinitely.
Wrong way to look at it. The hose should be replaced every 10-15 years no matter what, as the hose itself can fail instead of the fittings. No real need to do fluid film or similar, they'll just need replaced again in 10-15 years given same environment.
Now the question is, what about the hard lines? They are due for replacement too, if they are factory bare metal rather than coated, unless some prior rust-preventative measure was taken on them to mitigate rust.
In this case, a more corrosion resistant material like CuNi line does make sense, because it's also easier to work with than steel, let alone stainless, and can be expected to outlast the 4 soft lines.
This has nothing to do with this failure and in a winter saltwater environment, uncoated steel line is going to rust through from the outside before the inside. Do change the fluid if you're getting brake sponginess due to moisture, but it's not the kind of ticking time bomb many people imply, unless you're pushing your brakes really hard.