Hi IceCold,
I would be very cautious using wire gauge or coil count as a way to determine the quality, durability, or value of a mattress because the foam layers above the innerspring are usually the weakest link in a mattress, not the innerspring itself, and the gauge of the wire and the number of coils is only one of many variables that can affect how a particular innerspring will feel and perform inside a specific mattress design and can be more misleading than helpful.
The total amount of steel in an innerspring would probably be a much more important spec that could be used to compare the durability of innersprings (although this would also be somewhat misleading) but unfortunately this isn’t a spec that mattress companies provide and again the innersprings aren’t the weakest link relative to the durability of a mattress anyway. There is more about the different types of innersprings in this article and in post #10 here.
The specifications you need to know to be able to assess whether there are any lower quality materials or weak links that would compromise and reduce the durability and useful life of a mattress are in this article.
Any type of blend of latex in the layers above the springs will be a very durable material although I would still want to know the type and blend of the latex so that you can make more meaningful comparisons with other mattresses.
In the case of polyfoam and memory foam then foam density is the single most important factor in durability and is what you would need to know.
With major brand mattresses (Sealy/Stearns & Foster, Simmons, Serta) it will usually be difficult if not impossible to find out the information you need to know to make an informed choice but in those much more rare cases where you are able to find out you will find that in almost every case they all use too much lower quality/density materials which will soften or break down much too quickly.
Phoenix