When our kid was in college, MrsJay and I would each fly with 2 or 3 empty bags twice per year.

In the fall, the bags would be full with a year's worth of clothing, etc. for the outbound trip, as we helped junior move into the dorm - the bags would go home empty with us, because college dorms had no place to store the empty luggage. In the spring, we'd fly back out with the empties and pack the dorm contents into the bags for the trip home.