[Mylon]

Why don't you just say cultural world centers aren't meant to be built at all and leave it at that? Sure, a homeworld that leaves all of its building to base space yards could maybe start turning a space port/resupply depot into a cultural world center from the second turn and it might actually see it done before the end game, but even then it would be pretty impracitcal as would take a huge number turns _after_ being built to make up for their huge cost through mineral production, research points, intel points, ect...

Even on ringworlds were conditions are always optimal and one really can drive a unmodified Honda (well, you'll still need paved roads) around, accomplishing such a task is nearly impossible.

Thinking in purely game mechanics (which, in my opinion have more say that realism, because if I wanted realism I'd play more real life), Cultural world centers are wasteful to build. Starting off with a bunch is a nice bonus, but to build one would lock a good planet's production for 500 turns and require an insane amount of resources, thus making them unpractical.

And, from another standpoint, consider that America was a colony some 300 years ago or so. People brought their culture with them and built rather quickly, about as much as population would allow. The two factors that limited America's growth were population and technology. Look how fast things grew when the railroads were built. Colonists don't loose their culture merely because they no longer are around their own culture, so if you bring along enough colonists then culture by itself is certain not a problem. The infrastructure (on the level of compactness as the colony world center) would be difficult, but you even noted how it can be done in 27 turns.