Hi klphoto7,
While this is the case with most of the major manufacturers that you will most often see advertised in the mainstream industry … it certainly isn’t the case with many smaller manufacturers that make great quality/value mattresses all across the country that I would normally suggest buying from anyway.
There is more about the mainstream industry change from two sided mattresses to one sided mattresses in post #3 here and there is more about the pros and cons of a two sided mattress in post #3 here and the posts it links to.
If you shop for a mattress in the way that most people do and focus more on the major manufacturers or chain stores and you don’t confirm that there are no lower quality materials in a mattress you are considering then the odds are much higher that you will end up purchasing a mattress that uses lower quality materials and has a significant weak link in the design (see the guidelines here along with this article).
There have been many changes in the industry in the last 15 - 20 years and it’s certainly true that many if not most of them are for the worse (see post #3 here and post #404 here and post #12 here among many others on the forum that discuss this).
I would need to know the specifics of the materials in any particular mattress to make any meaningful comments about it but it’s very likely that the mattress you own uses both higher quality and more durable materials than many of the mainstream mattresses made today and of course being two sided will also be more durable than an equivalent one sided choice.
There aren’t any “studies” that make apples to apples comparisons between the durability of the many thousands of different combinations of materials and components that are used to make mattresses and the durability and useful life of a mattress is also relative to the specific person sleeping on the mattress and how long it takes before they cross the thresholds from sleeping well on a mattress to sleeping “OK” to “tolerating” a mattress and then finally deciding to replace it and this can vary widely between people.
Having said that … there is more about the many variables that can affect the durability and useful life of a mattress relative to different people in post #4 here and the posts it links to.
There is also more about the most important parts of the “value” of a mattress purchase in post #13 here (including durability) that can help you make more meaningful comparisons between mattresses.
If you haven’t read it already … the first place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
Phoenix