I have a one story house with a 60 foot hallway. The drywall ceiling cracks whenever the weather turns cold and wet. I think the problem is that the framing members above the ceiling absorb moisture and swell, and I don't think settling is the problem (the house is seven years old).
The contractor brought in an "expert" (who did not agree with my "expert") and extensively repaired the ceiling four times. He also improved the truss structure supporting the roof tiles. He put in an expansion joint to control the stresses, but a crack developed within 2 feet of the joint in about a month. He doesn't have a clue!