Full size for a second home, meaning it is only used 3 to 4 months a year. Bought a new non hybrid about 8 years ago. After a year or so it started to ‘sink’. No longer comfortable… just too soft. Researching hybrids we have sort of settled on a BeautyRest Silver 12" hybrid in Extra Firm. Extra Firm mattresses seem to be very hard to find. But I now worry as a hybrid it will… 1/ Not remain firm 2/ Not have a sturdy edge. At home we have a Serta Prestondale but have no idea what firmness it is. But we did need to add a topper so it likely is at least firm but not a hybrid. Does anyone know the specs of the Serta Prestondale? Knowing the number of coils and type of comfort level foams might help us find a similar mattress now. One thing we have learned… we want a tight top not a plush. But like extra firm that type of top seems to no longer be popular. Suggestions?
Hi capecodbeachfront.
Welcome to our Mattress Forum. 
The sagging, sinking, and premature softening are indicative of the foam materials breaking down. Any mattress can feel good in the showroom but the durability and the quality of the materials and components within the mattress is what determines how long you will sleep well on it. You are quite fortunate that after using a sagging mattress for 7-8 years you are not experiencing lower back pains and sleepless nights.
As you are in the market for a new mattress, if you haven’t done so already, definitely take a look at our Durability Guidelinesand dismiss any mattress for which you do not know the thickness, density and IFD/ILD
we have sort of settled on a BeautyRest Silver 12" hybrid in Extra Firm. Extra Firm mattresses seem to be very hard to find. But I now worry as a hybrid it will… 1/ Not remain firm 2/ Not have a sturdy edge.
Generally speaking, the major manufacturers and brands (such as Sealy/Stearns & Foster, Simmons, and Serta) all tend to use lower quality and less durable materials in their mattresses than most of their smaller competitors. These materials and components in their mattresses will tend to soften or break down prematurely relative to the price you pay which is why I would generally suggest avoiding all of them completely (along with the major retailers that focus on them as well) regardless of how they may feel in a showroom along with any mattress where you aren’t able to find out the type and quality/durability of the materials inside it (see the guidelines here. along with post #3 here. and post #12 here. and post #404 here).
You did not share any of your stats with us so I am not able to determine if there a particular reason you’re seeking out an extra firm mattress? What led you to this particular BeautyRest?
They are listing the following comfort Layers:
1" AirCool Foam
.5" Plush Comfort Foam
.5" Dynamic Response Memory Foam
2" Firm Comfort Foam
Support System:
900 Series Beautyrest® Firm Pocketed Coil® Technology
Their proprietary ingredients are listed without specific details on the materials themselves, important for evaluating a mattress’s durability long-term. Also, BeautyRest mattresses have the “Beauty Edge” which just means that the outer edges of the mattress are reinforced to make it more stable when you sit on the edge of the mattress, and so you don’t roll off if you sleep to the edge of the bed. If the foam density is low then the foam perimeter itself is subject to breakdown over time.
Serta Prestondale is a discontinued line up and even if you would know the specs, attempting to find something that is exactly the same is often a frustrating and futile exercise especially if you are trying to do this on your own. There is more information in post #9 here about the different ways that one mattress can “match” or “approximate” another one.
Every individual layer and component in a mattress (including the cover, FR barrier, any quilting material, and of course all foam layers) will affect the feel and response of every other layer and component both above and below it and the mattress “as a whole” so you would need to carefully asses the design and the specs of each mattress that uses exactly the same type of materials in order to determine if that the mattress in its entirety will be a good “match” for you in terms of “comfort”, firmness, and PPP(Posture and alignment, Pressure relief, and your Personal preferences) This is especially important when you are trying to approximate the mattress you are considering with others that use the same type of materials and components which may be just as durable but have a different design or firmness level that may be completely unsuitable for you to sleep on.
“Specs” about each person’s body type and sleeping position are an important part of how each person interacts with a mattress but there are many other variables as well. There are many different types of layering combinations that can perform equally well for people of a certain height and weight and sleeping style so the most “accurate” way to “fit” a mattress to each person is to work with a knowledgeable local person who has the experience and knowledge to help you make the most suitable choices in “real time” and in person. There are some general weight and height guidelines here and some general guidelines about sleeping positions here and some information about how different types of layering can change and affect these guidelines in this section of the site but these are general guidelines and starting points only and will do more to help you know who has the knowledge to help you make the best choices more than they can be used to design or recommend a specific mattress based on what I call “theory at a distance”.
The first place to start your research is the mattress shopping tutorial here(there is a condensed version of it at the end of that post) which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps, more importantly, know how and why to avoid the worst ones. 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”, firmness, and PPP 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 he will sleep), durability (how long he 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 (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
I hope the information provided will put you on the right track and help you find a suitable mattress.
Phoenix