Why warships exceed their peacetime speed limits

What explains apparent plot speed when warships exceed their normal rated performance?

Wartime commanders may push boilers and turbines beyond safe peacetime limits when the target matters and a major refit is already due, accepting machinery damage that routine operations would avoid.

Boiler ratings include safety margins, and commanders may consume those margins when an important target must be caught. A ship already headed for major machinery replacement has even less reason to preserve worn burners, tubes, or turbine blades. The same logic applies to firing across decks or over lower turrets: peacetime restrictions protect equipment and budgets, while combat accepts local damage to land the necessary shot.