At what point is it no longer cost effective to keep old ships in service?
Short answerThe choice depends on whether the capability is still needed, whether a new class is justified, and how much new technology should be inserted at once.
NotesRetirement depends on whether a navy still needs a ship's capability and whether a new class is preferable to continued maintenance and upgrades. The Ford-class example concerns a necessary carrier replacement complicated by decisions about how much new technology to include. Zumwalt illustrates a related criticism of requirements concentrated on supporting land operations. The counterproposal is a more general-purpose ship with more missiles, an advanced gun system, and a broader radar suite. In that scenario, a sustained Zumwalt program might have changed the later demand for a new large surface combatant. A cheaper supporting class could then provide additional numbers.