In addition to affecting your comfort, firmness also influences other important elements relating to the performance of your mattress, including the following:
Sleeping hot: too much sink or contouring can limit airflow around the body. This can cause heat to build-up in the mattress and on the skin, which is also known as “sleeping hot.” This is primarily an issue with plush mattresses and those that are made with certain materials (especially memory foam) that more closely contour to the body. Of course, the mattress ticking plays a big part as well.
Sex: mattresses that are extremely plush or extremely firm may pose barriers to frequent sexual activity. If a mattress is too soft, partners may sink into it too much, preventing movement on the bed. If it is too firm, it may be very hard to comfortably assume many sexual positions. In most cases, a medium to medium-firm mattress is best for facilitating sex.
Motion transfer: this refers to how much movement on one side of the bed is felt on other parts of the bed. A bed that allows a lot of motion transfer may cause people who share a mattress to be awoken or disturbed by the movement of a partner. A very firm mattress that does not respond much to the body’s movements at all also usually will not have much motion transfer. The level of motion isolation is also directly affected by the type of material used to build the mattress. Going for Individual Barrel Pocketed Spring systems would be one effective way of avoiding motion transfer.
Edge support: for people who regularly sit on the edge of the bed or sleep near the edge, edge support is an important consideration. Remember that most mattresses are weakest at the edge, so if a mattress is already quite plush, it is likely to offer a less supportive “seating” at the edges. People who prioritize edge support usually should err toward a firmer mattress overall.