Half of good strategy here will depend on what type of game you're playing. If you're playing a diplomatic, cultural, or possibly space game with not all too much territory, then you'll probably want to max out your shields over time i.e. plant and chop every possible square. Same goes for really any 5CC, OCC, or XCC where X doesn't get too large. On the other hand if you have an empire which swells over some 20% of the domination limit, then worker turns start to get scarce.