Hi,

Some mattresses require a 'break in' period. These are typically new (hopefully you bought a new mattress!!) mattresses, that are not compressed for online sale, fresh off the line. Some quickly lose up to 20% firmness within 6 months, some do not. It just depends on the quality of the materials, springs (sadness), foam, whatever.

One advantage of a compressed mattress is that it knocks out the 'break in' period during the compression process. So each mattress will feel more like to floor model in the store. Compressed mattresses, by default (I mean high quality) require a higher quality foam that can withstand the compression and still be durable over many years. Compress most showroom mattresses and it would never recover because the materials could not withstand it. This indicates failure over time in my opinion.

Another thing to note, a separate issue, is a break in period for your body. This may happen due to your body adjusting to its new sleeping surface. Typically this only lasts two weeks and depends on a number of factors including health, weight, prior sleeping surface, body type, and age. You may not like your new mattress at first but your body will adjust to it over time.