In VB6 Aurora, there is general consensus that the NPRs are not great at research so they present less of a challenge over time.
In my current game, which is seven years in, all four NPRs have researched the next generation of engines, designed new and larger ships, retooled shipyards as they become available and began building the new designs. They have both generations in service which adds a lot more variety to NPRs ships and also means the ships you meet on the frontier may not be the latest designs. One NPR has just researched its third generation of engines and designed a third generation of ships, although it hasn't retooled any shipyards yet. I have only just researched my first set of new engines so they are getting ahead of me.