Why modern warships serve longer

How long do modern navies keep ships in service?

Often longer than in the past, because machinery and electronics can be renewed while a sound hull continues to serve.

The Royal Navy once expected about twenty years of service from a warship, while modern hulls often remain in use longer. Internal systems, engines, and electronics can be renewed so long as the hull remains viable. Major changes in hull form are rarer when no large naval war forces rapid experimentation, with tumblehome offered as a possible future shift. The comparison is the long transition before ironclads became dominant, when important changes emerged without sustained peer war at sea to force adoption.