Hi Djehuty,
ILD is a “comfort spec” and wouldn’t be an issue in my choice or in terms of durability.
While its true that softness is a secondary factor in the durability of all foams (including latex) … the suitability of a mattress and the layering is much more important and latex is a durable material in any softness/firmness level compared to other types of foam and there would be little point to choosing a firmer mattress for the sake of any gains in durability if you can’t sleep well on it because it’s too firm.
I also don’t know the specifics of the rest of the mattresses you listed because you only included the top layers of latex and the rest of the mattress would make a difference as well. If your second and third choice has the same thickness and type of materials besides just the top 4" of latex then I don’t know why they would have a different price.
If you could include all the materials and specs of each mattress from top to bottom it would be helpful in terms of helping you identify any potential weak links in any of these mattresses.
The suitability of a mattress is not an issue of the materials but of the design of the mattress and how suitable it is in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). There are two basic needs in a mattress which is to keep your spine in neutral alignment in all your sleeping positions and to relieve pressure and this is true for anyone regardless of any back issues they may have. Beyond this you are dealing with preferences that you can also include in your testing or with knowing the quality and durability of the materials (which you can’t feel in testing). Only your own testing and experience can answer which mattress design is best for YOUR back, body regardless of how well it may work for anyone else. There is no “one size fits all” solution in a mattress for back issues either in terms of material or in terms of design. There is more about this in post #2 here and in post #4 here about your “perfect” mattress.
There are 3 main types of foam used in mattresses. These are polyfoam, memory foam, and latex. Tempurfoam is a specific brand of memory foam used by Tempurpedic and there are many other memory foam manufacturers that use other types of memory foam or gel memory foam in their mattresses and there are also many mattresses that don’t use memory foam at all in any of the layers (using either latex or polyfoam). The key with any of these is to make sure the specific design works well for you in terms of PPP and that no matter what type of foam or other materials or components it uses that it’s high quality and durable so the feel and performance of the mattress is more likely to last for many years without the loss of comfort and support that comes from the early breakdown or softening of lower quality materials.
When you purchase a new mattress there will be an initial break in period where that materials soften and lose any “false loft or firmness”, the materials settle, and the cover also stretches and loosens to some degree. Most of the mattresses you test in a showroom will already be broken in from people testing them but you can always ask if they are new or have been on the floor for some time. If the floor model is new I would “expect” that it will be slightly softer when it’s broken in. If its already broken in then I would expect that the mattress you receive may feel a little firmer for the first 30 - 90 days or so (usually less than 30) but will end up being the same as the floor model.
In addition to this … it will also take some time for your body to adapt to a new sleeping system and “unlearn” the sleeping habits that have developed over the course of years of sleeping on a different type of mattress. If you have done some good and “objective” testing in the store using the guidelines and confirmed that a mattress is suitable for you in terms of PPP then there will usually only be some temporary discomfort if it even happens at all (some people don’t go through any adjustment period at all and are happy with their choice from the first day). If your sleeping posture on the mattress is good you will be adapting to good posture and alignment in other words but it may take a little time for your body to get used to better alignment. This is much like when you have an illness and sometimes symptoms can get a little worse when they’re treated before they get better as part of the natural process of healing.
If for any reason you are uncertain about your choice then the return or exchange policy may be an important factor in the “value” of your mattress purchase and your personal value equation. If several choices appear to be “equal” in terms of PPP then I would tend to err on the side of firmness because it’s always easier to fine tune a mattress that is too firm using various types of mattress pads or a topper than it is to make a mattress that is too soft any firmer because this would involve removing and replacing individual foam layers. Good testing will usually be “close enough” that only fine tuning and minor changes that don’t involve the mattress are necessary. There are also many local manufacturers that can replace an individual layer in a mattress and some component mattress designs that have a zip cover have the ability to re-arrange or exchange individual layers as well but without one of these options or making a choice that was “close enough” based on your testing you would be dependent on exchanging a complete mattress or returning it for a refund (if either of these are options with the retailer or manufacturer you are dealing with) if you make a choice that is less than your ideal.
The key is always your own confidence in the “accuracy” of your testing because in the end nobody else can feel what you feel or predict with absolute certainty how well a mattress will work for you more accurately than your own personal experience either in testing a mattress or sleeping on it after a purchase.
Phoenix