Pathfinding in city builders. Store the paths?

Hi In a game like stronghold with many workers going back and forth from a workplace to a dropoff-point for example, would I store the path and then use it backwards to not have to redo pathfinding all the time? If the moving units in the city doesnt block movement, very often I could just reuse the old path. Only if i run into a wall (if the player constructs a new building in the path of the old workers) will I recalculate the path. Workers in old age of empires for example, do they pathfind every time they go back to drop off gold in the storage? Thanks! Erik