^ Memory foam is also very sensitive to temperature from a firmness perspective. I remember a number of years ago we drove up to visit the in-laws during the winter. My wife threw her memory foam pillow in the trunk and by the time we got there it was a brick. Took a good 48hrs+ to soften up again. I have shoulder pain with memory foam as well... doesn't seem to be the right type of support for side sleepers, not sure why it would matter, but I have never been able to get use to the Tempurpedic at my in-laws.