A quirk of Traveller ship design is that considerably earlier TL vessels don't become redundant. We're not talking about an age of sail craft vs an Aegis cruiser. Ships are effectively useable after what would be hundreds of years after their production date if you were to compare technology time lines. Becoming outdated is really by the game design only a difference in M-Drive and Jump capability. Offensive fire power doesn't change that much in the sense if you're a 10,000 ton craft you're still going to be seriously out gunned by a 20,000 ton craft 3 tech levels below you.
Which then implies a simple issue of refit and resupply to brown water navies of older designs...
Which then implies a simple issue of refit and resupply to brown water navies of older designs...