Why does a mattress lose firmness over time?
A mattress can feel softer for more than one reason. Comfort materials can change how the surface feels, and repeated load can also change the deeper support structure. Those changes can happen together, so a softer feel by itself doesn't tell you which layer changed.
A mattress that felt firm when it arrived can feel noticeably softer later on, and it's hard to tell whether that's ordinary settling or something that will keep going.
Two kinds of softening.
The comfort layers are the foam near the surface. With use, they settle and lose some of their original firmness, which changes how the bed feels when you first lie down.
The support core is the coil unit or dense base underneath. Under repeated load it can change too, and that affects how the mattress holds you. Sagging vs. body impression vs. break-in sorts out the early changes that are normal.
Why support can change before you see it.
A mattress can lose support before it looks broken: repeated compression can create material fatigue in high-load areas, often including the load-bearing center third, so support can fade before visible sag appears.
That's why a bed can feel different while the surface still looks level. Why does support loss happen before you can see it? goes into the materials side.
Is it the surface or the support?
Where the change shows up is useful information, but it doesn't identify the layer by itself. Comfort materials and the deeper support structure can both change in the area you use most. Compare the center with less-used areas, look for visible impressions, and check the base before deciding what changed. Is it your mattress or your foundation? explains the base check.
Does a firmer mattress keep its firmness longer?
Not necessarily. A firmness rating describes how the surface feels when it compresses. How long support holds up depends on how the complete build handles repeated load, including the load-bearing middle, and a firm-feeling mattress can still develop uneven support loss. Does a firmer mattress mean better support? covers the difference.
What you can do about it.
If the support underneath is sound and the change is mainly in feel, a topper can adjust how the surface feels. It can't restore support that has changed underneath. My mattress sags in the middle: topper or replace? covers the warranty and replacement side.
In short.
- A mattress can feel softer because of changes in the comfort layers, the support underneath, or both.
- Where the change shows up is a clue, not a diagnosis of which layer changed.
- A firmer rating doesn't by itself tell you how support will hold up.
Related questions.
Is a mattress losing firmness the same as sagging?
Not necessarily. A softer feel can come from the comfort layers, the support underneath, or both. A sag is a dip you can see in the surface, and it often involves the support.
Can a mattress's firmness be restored?
A topper can change how the surface feels on a structurally sound mattress. It can't restore support that has changed underneath.
How long does it take for a mattress to soften?
There's no single timeline. Materials, construction, body weight, use, and the base can all affect how a mattress changes.
Essential™ and Signature™ use StasisLayer™, with a reinforced center third. The three main coil zones use 2.0 / 2.3 / 2.0 mm wire, and the comfort surface above them is continuous, not zoned. → See Signature