Hi Andy650,
Unfortunately all the major brands (not just Sealy/Stearns & Foster) tend to use lower quality materials in their mattresses than most of their smaller competitors that will tend to soften or break down prematurely and I would avoid them completely (see the guidelines here along with post #3 here and post #12 here and post #404 here).
The “luxury” is just marketing stories.
If I was in your shoes I would go for the refund so you can start again to find a much better quality/value mattress since if you just replace your mattress with another mattress made by a major manufacturer you would probably just be replacing one mattress with lower quality and less durable materials with another one.
You can see some comments about Saatva (and some of the other "simplified choice online mattresses) in post #2 here and as you can see I would be somewhat cautious here about the quality and durability of the materials that they use. A forum search on Saatva (you can just click the link) will bring up much more information and feedback about them as well. I would be very cautious about buying any mattress based on “marketing information” that is on a website.
I would keep in mind that while other people’s comments about the knowledge and service of a particular business can certainly be very helpful … I would be very cautious about about using other people’s experiences or reviews on a mattress (either positive or negative) as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you and in many if not most cases they can be more misleading than helpful because any mattress that would be a perfect choice for one person or even a larger group of people may be completely unsuitable for someone else to sleep on (see post #13 here).
The first place to start your research is the mattress shopping tutorial here which includes all of the basic information, steps, and guidelines that you will need to make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones (including the major brands and the stores that tend to focus on them)
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists (based on all the parts of your personal value equation that are most important to you).
Once you reach step 3 in the tutorial if you let me know your city or zip code I’d be happy to let you know about any of the better options or possibilities I’m aware of in your area.
Phoenix