A navy introduces new technology alongside the forces it already owns. Forecasts that a weapon will become obsolete in twenty years do not make it obsolete immediately. Existing systems can continue to provide useful service throughout much of that interval. Replacement decisions need to account for the time required to develop and field the successor, as well as the capability lost by retiring equipment early.
Notable Point · 1:57:42-1:58:56
Why future obsolescence does not justify retiring useful ships now
A replacement expected in twenty years leaves an existing system with years of useful service before the transition.