Any mattress, including a king mattress, should be flipped every two to three weeks in the first three months of use. Following that, the mattress should be flipped every two to three months. Box springs can be rotated, but not flipped, every six months.
Flip mattresses to ensure the best possible sleep. If mattresses are not flipped and rotated, they may develop body impressions. Flipping and rotating also help to extend the life of the mattress. King-sized mattresses may require two people for flipping, since they are large and heavy. With a king mattress, it is also important that the bed frame has a center support that prevents breakage or bowing.