Turn 60 should be about right time for the serious fighting to start. That doesn't mean someone won't try a raid or two earlier, but they would leave themselves very vulnerable to counterattacks if they go before the defences are ready.
As to shipyards: Build bases, lot of bases. The amount of resources this game will produce is incredible. The planetary SY's can only utilize a fraction of what all these planets can produce. In RTH-1 I had about 2000 BSYs, and I am sure a fully developed RTH-2 home cluster can support at least 1000
BTW: Mineral Scanners are better than Robotoid factories. With the new patch you get +45 %
