I usually start all 5 and do things a little differently in each. Typically at least one won't make it.
Once they get going (everyone trained in something and set to a task), they can be left alone for an hour or two with no harm. Until I have a big population and unlimited food supply, I pause if I'm going to be away from my computer for longer than that.
In VV3 I only started 4 tribes so that there will be two for each faction, and I'm saving one to do on "hard" setting later, using the faction I decide I like best.
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Runners... never enough runners....