Hi Helen,
Your experience is certainly unfortunate but is also much too common when there is so little information available to consumers about how to make an informed mattress purchase. The first place I would start your research for a new mattress is the tutorial post here which has all the basic information, steps, and guidelines you will need to make the best possible choices … and know how and why to avoid the worst ones (including the major brands such as Serta and most of the mainstream retailers such as Mattress Warehouse).
The industry was very different 17 years ago and it’s much more common to find lower quality and less durable materials and designs now than it was then (see post #3 here and post #404 here).
If you follow the steps in the tutorial post one by one you will have a much better chance of making a great purchase that will be suitable for your specific needs and preferences in terms of PPP and will last you for many years.
If you let me know your city or zip code I’d also be happy to let you know of any of the better options or possibilities I’m aware of in your area.
Phoenix