My dad had a rule which makes a lot of sense for travel planning. The rule was:
Spend twice as long in the destination as it takes to get there.
I have at various time discussed this rule with my brothers and it have been unclear if this rule should be interpreted to mean all travel time against stay time or just travel time to the destination.
Considering my kids and family a modification seems to be in order:
We need to think in two week chunks. Less than two weeks in the same place breeds anxiety four our group. Additionally, our family takes at least three days to recover from jet lag.