As an engineer it does get depressing to know that almost every man made structure has an expiration date.
Structural components require regular inspection.
One day those inspections will turn up a need for repair that's more costly than the residual value of the structure.
Arecibo was a unique case because they couldn't even figure out how to do the repairs without endangering the whole structure and thereby endangering the workers who were attempting to repair it.
luckily the structure was always getting detailed attention from some of the best engineering minds in the world, so they were able to figure that out before they put anyone's life at risk.
Contrast that with like the I-35 West bridge in Minneapolis. Some of the lanes on the bridge were closed. The worker attempting to repair the braces under the bridge deck probably would have been safe, if not for the fact that the contractor decided to park some heavy equipment on the closed lanes.

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