The best memory foam mattress solution is manufactured from polyurethane foam or low resilience polyurethane foam. Your mattress is created with a higher density memory foam that softens with your body heat and allows your body to mold to the warmed foam in minutes. This type of mattress has a faster speed of recovery to its original shape after your weight has been removed. This is named a newer generation of foams with faster recovery qualities.
The edges and sides of a mattress are potential weak points that tend to give way first. Many of the better more comfortable and durable mattresses have reinforced sides that resist sagging and maintain their strength as they age. The effective life of a mattress can be extended by regularly turning it end for end and also reversing the sides. This tends to even out the deformation of the springs with age and use.