I start the game on normal speed as the villagers eat less food than on 2x speed. They can usually build up a good store of food quite quickly. Once I've over 500 I'll put my farmer on another job; the kids usually keep the food topped up by finding mushrooms. It's important to remember to put the farmer back if I leave the game, though; otherwise the villagers are in danger of starving without any mushrooms from the kids.

The figure of 500 is only to provide a safe margin. A lower figure would probably work perfectly well, but it's better to be safe than sorry. I'll keep watch over the food counter and if it shows signs of dipping very far below 500 I'll put back the farmer.

Once I've built the dam I'll switch to 2x speed. The villagers won't have so long for the first crops to appear, and they usually have the first baby about then. I can't stand waiting for the two hours it takes for a baby to stop nursing, let alone four hours on normal speed!

I'll generally play on 2x speed for the rest of the game until I've completed all the puzzles. Around then I'll start another game which means I can't give this game so much attention. At that time I'll switch back to normal speed.
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To err is human; to arr is pirate.