Hi eek,
The materials in a mattress will soften, compress, or break down faster under the heavier or more weight concentrated areas of the body than under the lighter or more recessed areas of the body so I think it’s a good idea to rotate or flip (for a two sided mattress) a mattress on a regular basis to even out the wear and softening as much as possible yes.
You can see the suggestions I would follow here.
Phoenix