When it comes to compressing a mattress as you questioned. One thing is the law label. Manufactures must list what materials were used, when the product was produced, and a lot of other information is contained on that label, sometimes down to the person who sewed the product together. Many companies, such as Brooklyn Bedding, and most BinB mattress versions used by our trusted manufactures, are made to order. So, YES, you go on the website, or brick and mortar store, and they make that mattress to order, compress it and ship it in short order, most of the time less than 2 weeks, from compression to your home. Others, like the ones I see in Sam’s Club and Costco, are more difficult to discern as they could be in that box for months, which speaks to your point. They must have that law label though, so you will eventually will have the information you need to make that compressed time evaluation, some put dates on the outside of the box. But don’t be fooled. Just above those BinB in Sams and Costco, are fully expanded mattresses either placed horizontally or vertically. You might want to ask or question some of those same concerns. Many manufactures glue their layers together…or not…and are not tufted, so when these mattresses are sitting on the sides for too long, there may be nothing to prevent any one of the layers, springs, or fabric to stretch, move or shift abnormally, even there you have a potentially bad mattress.
Compressing is not always a bad thing, although I am sure I will get heat for saying it. Springs in a mattress are very predictable and can be made to fairly consistent tolerances, tensile strengths, specific resistances and weight supporting characteristics. If you have ever taken a physics class, you know what I mean, (I am 63, so I can say, “they made me do it, they made me do it”) not sure what classes they make you take in high school and college these days, but I had to whether I liked it or not. In any case, when you compress a compression spring down to its “solid” form, it can actually increase the resistance and performance of that spring, but if you leave it compressed for too long, the spring can fatigue and become weaker and have a shorter life span. This is why you don’t want to leave a mattress compressed for too long. I like to believe (and I might be a little pie in the sky about it, because I am that way in our own practice) that quality companies are not worried that their product is too good and lasts too long. I think they actually thrive and are proud of it. When I have a patient who buys a $1000 eyeglass frame, that can last them a very long time, they are usually the same patients that come in the next year and buy another one, rather than reuse their year-old super quality great frame. Funny how it happens, but it just does. Now most folks don’t buy a new mattress because they want to change their “style” like a pair of eyeglasses or a woman with an expensive handbag might. For some, though, as we get older, have medical issues, changes in weight, and so on, our requirements change for the type of mattress we may feel comfortable with. When this happens, where do we turn? To the quality manufacture or store where we bought our last mattress that gave us years of service and now due to no fault of the mattress, we simply need something different. So, unlike the “copycat” players who want to capitalize on mimicking someone else’s quality product with a poor excuse for a generic replacement, although it is tempting, may be here today and gone tomorrow to make a fast buck, the manufactures who have stood the test of time, without diminishing the quality of their product, I believe will always win out. I won’t speak to the brands and some of the more famous names we have known and loved for years, but in some cases, they have left their quality at the door, in place of the race to the bottom to compete with the abundance of wannabes into the market place, as the profit component, in some cases overshadow the quality component. I remember when certain brands of products we the best in their respective industries, and due to profit margins, competition, end up being run of the mill box store brands rather than the premium couture brands of their “heyday.” In any case, sorry for the long boring post, and any grammatical errors. But I hope I covered most of what you are thinking about.