Can a topper rescue a mattress that is too firm, or am I just paying twice? Topper

Bought a $180 memory foam topper for a too-firm bed. It worked for about seven months and then developed a permanent trough where I sleep, and a trough on top of a firm mattress is worse than the firm mattress. Latex or wool cost more and hold shape; cheap memory foam is a rental, not a repair.

Topper fixed exactly this for me and the reason it worked is your weight. At 55 kg I was never going to compress a hybrid's comfort layer, so I was sleeping on the springs' response rather than the foam's. A 7 cm latex topper gave me a layer soft enough that I actually sink into something. A 3 cm one did nothing at all — I tried that first and wasted the money.

It moves the problem if the mattress is too firm because the support core is wrong, and it fixes the problem if it is too firm because the comfort layer is thin. Yours is eleven months old and firm from day one, which points at the second. Rule of thumb I use: press down hard with a flat palm. If you feel springs within about 4 cm, a topper will help. If the whole thing is uniformly rigid to the depth of your hand, it will not.

Something cheaper to try first: a wool mattress pad, the thick unquilted kind, is maybe a third of your budget and takes the hard edge off without changing the support. It did not solve everything for me but it made the bed tolerable while I saved for the real fix, and I kept using it afterwards for warmth.

Heat warning, since nobody mentions it until it is too late. Adding 7 cm of dense foam on top of a hybrid removes most of the airflow you paid for. If you sleep warm, buy latex with pinholes or wool, not solid memory foam.