Except on rare occasions, boundaries for congressional and state legislative districts in the united states are redrawn by the states every

The correct answer is 10 years

This is because every 10 years there is a census where it is seen how many people live in each state, and more precisely in each district, and then the districts are redrawn. Rare occasions include things like preventing gerrymandering or other illegal activities that make the district boundaries biased in any way.