20-30 SECONDS? Wow, you're quite fortunate. Mine often take 20+ minutes to run. Basically, all you can do is try to minimize the number of ships moving on autopilot. Fleet up ships in transit if they're all going in the same direction, that sort of thing.

20-30 second turn time? Wow! What processor are you using? 

I have a Intel(R) Core(TM)2 Duo CPU T5750 @ 2.00GHz with 3gb of memory and it still takes over a minute on later turns in an immense galaxy.

If you can turn around in 20 secinds with a few hundred ships etc then yo uhave a really good rig there!