Biggest problem age of war era was not that people were building up war fleets they were building nations.
Maybe the CC, but the FWL had been around since 2271, the FS since 2317, the DC since 2320, the LC from 2341 and the CC from 2367. Most of the states should be past the nation building period when the age of war breaks out. Even the CC should be in decent shape- the individual states were fairly developed, even if the CC as a whole was not fully integrated.
FR FedSun points to that with Federated Boeing being built
I'm not sure what this has to do with the discussion at hand. The FS had major shipyards at Delevan, Kathil, Panpour and Layover as well as other yards at New Avalon, New Syrtis and Markesan, representing a fairly strong and healthy aerospace industry. The Galax Fed-Boeing facility according to earlier material wasn't built until 2781, when Boeing Intersteller, in the wake of the Coup, sought to expand outside of the TH. Even if TPTB change the date so that it is being built in 2765, the reasons for the expansion are still valid, seeking to remove all of their eggs from the one basket they are in.
I think you'd probably find half a dozen WarShips as the poster child's for the navy but the vast amount of production going on jump ships connecting the realms together. In the early years I don't see the Succession States as stable entities instead I see the Lords fighting the PR game to keep there nations together. To do that you need jumpships and solid lines of communication
Yes they need Jumpships for communications, but according to sources Franco Liao had a fleet of over 1000 merchant ships, not the CC, Franco Liao. Jumpships were plentiful. And by the 2400s the nations were fairly stable, yes you had events like the Davion Civil War, but is that really any different then the FC civil war? or any of the FWL civil wars? Beside warships are a way to project power. If a world wants to rebel you just place a warship in orbit and blockade it (yes easier said then done) and orbitally bombard anyone who is a threat. Just having warships able to travel around on a regular basis showing the flag will remind worlds that they need to stay in line (more important for the DC and CC then say the FS)
Also it just doesn't make sense that you would invest so much in the infrastructure needed to build warships, build 6 and then stop. Why even make the investment in the first place.