A high copper content does not necessarily mean a longer useful lifespan. Anti fouling paints are formulated to release biocide at an unalterable proscribed rate. However, more biocide does typically mean the paint will be more effective. Although even that is not written in stone as paint manufacturers are finding ways of making less copper work better.
As a rule of thumb, high copper hard paints (think: Pettit Trinidad) will provide good anti fouling performance longer than ablatives of any type (like your Pettit Hydrocoat.)
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