Hi Napper,
Some mattress companies do durability testing on various combinations, others rely upon durability studies by the component suppliers, others do no durability testing, others rely upon their experience in construction, and others construct more upon initial comfort and appearance. As a consumer, you don’t know what a particular company may or may not have tested for, and even if they did, there is no one standardized test for mattress durability due to the many variables involved.
You mention “quality materials”, but a 3 lb (I’m assuming you mean memory foam), would not be what I consider a higher quality material. You can feel initial comfort, but you can’t feel durability or quality, which is why I recommend to know the layers on the inside of the company, as that is the only way you can more objectively evaluate and have an idea of durability and consistency of comfort. And a company’s “reputation”, such that you might be able to objectively determine, certainly can be an important part of one’s personal value equation when selecting a mattress.
Yes, higher quality materials will generally provide a more consistent and longer comfort life.
The reputation of a company (however one might be determining that) has nothing to do with the quality of componentry, nor does the price point. The most reliable way to assess the quality and durability of a mattress regardless of the “reputation” of the manufacturer on the label is to make sure you know the type and quality of all the materials inside it so you can identify any lower quality materials or weak links in the mattress.
It’s always more realistic to think of about 10 years as a maximum reasonable expectation for any mattress no matter what the quality or durability of the materials and then treat any additional time after that as “bonus time” because after about 10 years the limiting factor in the useful life of a mattress will often be the changing needs and preferences of the person sleeping on the mattress and even if a mattress is still in good condition after a decade … a mattress that was suitable for someone 10 years earlier may not be the best “match” any longer.
Having said that … with higher quality materials throughout a mattress and/or for people whose needs and preferences or physical condition or body type hasn’t changed much over 10 years then “bonus time” or even “extended bonus time” with higher quality/density and more durable materials like latex or higher density memory foam or polyfoam or natural fibers is much more likely than with less durable materials, which can often lost comfort after 3-4 years.
Warranties only cover specific manufacturing defects in a mattress and not the gradual (or more rapid in the case of lower quality and less durable materials) loss of comfort and support over time that is the real reason that most people will need to buy a new mattress. In other words … mattress warranties have little to nothing to do with the useful life of a mattress or how long one will sleep well on it.
The narrative of a product having a long warranty and the name of the company being recognizable has kept many salespeople employed and stores in business that offer poorer quality mattresses and ones that use lower quality materials. People purchase a new mattress to hopefully achieve quality and consistent sleep for as long of a period of time as possible (the most important part of the value of a mattress), as opposed to frequently replacing an “adequate” product which may or may not qualify for warranty replacement.
Warranties have nothing to do with comfort and durability – they’re simply guarantees against defects in workmanship. If one selects an item using better quality materials, there should be less chance of the product developing defects that would cause for a warranty replacement, instead of choosing something that uses lower quality materials that initially “feel good”, with the expectation that if it fails you might be able to get a replacement (again, comfort preference isn’t covered by a warranty). Selecting a product upon the expectation that it will need to be replaced (but might have coverage) isn’t what I recommend, but instead I’d choose something using better quality materials that most likely won’t fail within a reasonable comfort life.
I’m often reminded of the funny scene on the movie Tommy Boy where they’re meeting with a parts supply company and the buyer wants a large guarantee on the side of the box, and the Chris Farley character says something along the lines of, “Hey, I can expletive in a box and slap a guarantee on it, but all it means is that I’ve sold you a piece of expletive in a box.” I’m not doing the scene justice. :lol: But he’s making the point of buying a quality product where the use of the warranty would basically be unnecessary, as opposed to a product that is of lower quality where you’ll expect to replace it (and perhaps qualify for a warranty).
This might be a bit longer and a more general reply than you were seeking, but the questions were a bit broad, so thanks for allowing me a bit of latitude in my reply. 
Phoenix
