Hi mnguy,
There is no specific schedule that everyone would agree is “best” but I would tend to rotate any one sided mattress 180 degrees every week or two at first to help even out any initial softening or compression during the break in period and then after the first 90 days or so do it monthly and then after about 6 months rotate it once a season. All of this is assuming that the mattress is symmetrical from head to toe and side to side. This can help any mattress soften or wear more evenly and extend its useful lifetime.
If your mattress is a side to side “split” mattress with a different firmness on each side of the mattress then you would only be able to rotate it if you don’t mind sleeping on the other side of the mattress each time.
If your mattress is a king size and you can rotate it 90 degrees inside your bedframe and you are OK that there will be a little bit of overhang on the sides and a gap in the head and foot area then this would allow the mattress to break in more evenly than rotating it 180 degrees. This is also assuming that your mattress doesn’t have head to toe symmetrical zoning in which case it should only be rotated 180 degrees not 90.
For a two sided mattress I would alternate flipping and rotating.
While it’s not “necessary” … for a component mattress with individual layers it can also make “some” difference if you rotate and flip the individual layers from time to time as well (perhaps once or twice a year) although layer flipping and rotating would probably make more difference in terms of evening out any premature softening or wear in the top layers and would make less difference with the deeper layers in the mattress…
If the Select Comfort foundation meets the warranty criteria of the manufacturer of the mattress then it would be fine in terms of support.
I would use the suggestions in the foundation thread here.
Phoenix