Hi bonepetit,
Thanks for taking the time to share your detailed comments and feedback and for letting us know what you ended up deciding … I appreciate it.
Most importantly I think you made a good quality/value choice … and congratulations on your new mattress
You’re certainly correct that an innerspring is a support layer but it’s also true that every layer and component in a mattress will also have some effect on the feel and performance of all the other layers and components above and below it and on the mattress “as a whole” and different types of innersprings have different properties that can affect whether any specific mattress that uses them will be a good “match” for the specific needs and preferences of a particular person.
Steel innersprings are generally a very durable mattress component but the quality of the foam above the innerspring is generally the weakest link of the mattress and innerspring mattresses that use lower quality materials in the comfort layers is the biggest reason for the early softening, sagging, and breakdown that you read about so often … not the innersprings themselves. An innerspring mattress with high quality and durable materials above the innerspring can certainly be a very suitable and durable choice and they are still the most popular type of mattress sold in the industry. Original Mattress Factory also uses higher quality/density and more durable foam layers than most of the mainstream manufacturers in the industry which is one of the reasons I think highly of them.
There is more about the different types of innersprings in this article and in post #10 here.
I’m looking forward to any additional comments you have the chance to share once you’ve received your new mattress and have had the chance to sleep on it for a bit.
Phoenix