The ship we've followed throughout most of Star Trek is the USS Enterprise that maintains the registry number NCC-1701 with a suffix change indicating linage. Does anyone have a really good explanation why other federation ships that have known long lineages don't follow this registry format? I can, to a degree, make sense of registry changes when the ship becomes an entirely different class. To that end I can understand rationalize why the Constitution Defiant is NCC-1764 while the most recent Defiant of the Defiant Class is NCC-74205. However, in my mind it makes less sense when a ship name jumps classes. To me it seems logical that once the name Defiant is established as a Heavy Cruiser, the name would always be recycled for use of another heavy cruiser (unless perhaps, heavy cruisers are completely moth balled). Can anyone give a better in universe explanation better then "They REEEEALLY liked the name and wanted to feature a ship with that name" ?