You should flip/turn your mattress at least every 3-6 months. The more often the better for comfort, support and longevity.
This gives the natural fibres a chance to rest and recover from the constant pressure. Most pillow top or memory foam mattress can only be turned, which can still help.
It’s important to check first if it can be flipped/rotated beforehand. If it can’t be turned, it’ll probably breakdown quicker then a flip and turn mattress.
