Hi Frustrated Mattress Shopper,
These are all good quality materials and it has a good insulator above the coils which are also good quality and strong so there are no weak links in the mattress in terms of quality/durability.
Your retailer will know if they are still making it if they can still order it but Comfort Solutions still makes the XL line which is among their better quality mattresses.
I’m not sure what further research you want to do on this mattress but knowing the quality of the materials and being able to test it for PPP is the most important part of any research outside of making comparisons with any of your other finalists that you’ve tested.
The Kansas City list here has the better options I know of in the area (including two factory direct manufacturers Hawn Bedding and Lebeda) that may have a similar mattress (high quality innerspring with latex and/or high quality polyfoam comfort layers) that would also be worth including in your research.
Phoenix