Hi CrankyCub,
[quote]For the last 16 years I’ve been sleeping on a Sealy Posturepedic from Costco, the name of which escapes me. It is the very firmest model they sold at the time (Kingston Firm sticks in my head, but I’ve been looking at a lot of mattresses). I’ve always had either a down-alternative fiberbed or featherbed on top, and have been a religious rotate/flip adherent.
A few things have changed over the years. I’ve become more of a side sleeper, and I’ve added a 3" memory foam topper under my side of the bed - I vary between “under the featherbed” and “over the featherbed”. I’m 6’1" and 275#, so I’m not exactly petite. I’ve got some neck issues as well - arthritis and bone spurs, a little bit of disc pathology. My biggest issue right now is that I wake up in the middle of the night with my arms having “fallen asleep”, and I’ve contorted myself into some weird neck position…
I’ve also added a husband, who is 6’4", 350, and has a multi-level discectomy and fusion with hardware in his neck. He’s a side sleeper, but he has a couple of quirks. One is that he loathes memory foam - it’s like his superpower - he can detect a mattress with an inch of memory foam in the cover like a bloodhound can track a fugitive. It’s uncanny. He hates it in hotel mattresses, he hates it when we stay with friends and family, he hates walking by a display of it in stores. I have to admit, my overnight experiences on Tempur-Pedic beds at a few luxury hotels that trumpet their use have been underwhelming - I feel like I’m going to the floor. Neither of us has enjoyed SelectComfort beds in our travels, either, so they’ve been eliminated.[/quote]
I would agree that your mattress is most likely well past it’s “due date” 
There have also been many changes in the industry in the last 15 - 20 years and many if not most of them are for the worse … especially when it comes to the major brands (see post #3 here and post #3 here along with post #12 here and post #404 here among others on the forum that have discussed this).
While I can certainly help with “how” to choose … I don’t make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and your Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more accurate than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
Hopefully you’ve already read the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps most 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” 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).
I would also keep in mind that as long as the materials in a mattress you are considering are durable enough for your body type and meet the quality/durability guidelines here … the choice between different types and combinations of materials and components or different types of mattresses (see this article) are more of a preference and a budget choice than a “better/worse” choice.
There is also more information in post #3 here and the posts it links to that would be helpful for those that are in higher weight ranges. While the process of how to choose a mattress would be the same … most people in higher weight ranges will generally need or prefer firmer mattresses (firmer materials will feel softer because you will sink into them more) and materials and components that are higher quality and more durable than those that are in lower weight ranges (the materials and components in a mattress will soften and break down faster for those in higher weight ranges than they will for someone that is in a lower weight range that doesn’t compress the mattress as much). I would be particularly cautious about mattresses that use more than “about an inch or so” of memory foam that is less than about 5 lb density or polyfoam that is less than about 2 lb density.
[quote]Which brings us to our current spot. We tried an Englander latex mattress and really, really liked it for the 15 minutes we were laying on it - I’d never considered a latex mattress before. We also tried a “Sweda” from Lady Americana Sweda and really really liked it as well. Both are approximately within the price range I’d anticipated for the project. I’ve also looked at latex offerings from the various manufacturers discussed on the site.
My biggest concern, though, is that we are both pretty portly and that it just seems counterintuitive that something inherently soft and spongy will last even a fraction as long as good old-fashioned American Steel. I would like to think that a purchase of this magnitude will sleep decently for ten years, given the topper replacements. Is that realistic given that we are on the upper end of the fat bell curve? He prefers the “Medium” firmness (28 ILD talalay comfort layer) and I seem to prefer the 36 ILD.[/quote]
There is more about some of the differences between a latex support core and an innerspring support core in post #2 here but the choice between them would really be a preference and/or a budget choice rather than a “better/worse” choice.
Latex is among the most durable materials or components in the industry and “in theory” most latex support cores would tend to be more durable than most innerspring support cores but in practice the difference is probably much less meaningful because the the deeper support layers or components in a mattress aren’t generally the weakest link in a mattress.
While there is no way to quantify how long any mattress will last for a specific person or predict exactly when you will decide to replace it because it is no longer suitable or comfortable for you (because this is the only real measure of durability or the useful life of a mattress that really matters) because there are too many unknowns and variables involved that are unique to each person … if a mattress is well inside a suitable comfort/support range and isn’t close to the edge of being too soft when it is new (see post #2 here) and you have confirmed that it meets the minimum quality/durability specs that are suggested in the guidelines here then it would be reasonable to expect a useful lifetime in the range of 7 - 10 years and with higher quality and more durable materials like latex or higher density memory foam or polyfoam (in the comfort layers especially) it would likely be in the higher end of the range or even longer and the chances that you would have additional “bonus time” would be higher as well.
There is also more detailed information about the many variables that can affect the durability and useful life of a mattress relative to different people in post #4 here and the posts it links to.
It would also be realistic to expect that with your higher weight ranges any mattress will need to be replaced more quickly than it would for those that are lighter.
There are some comments about edge support with latex or other foam mattresses in post #2 here and the posts it links to.
There is more information about wool toppers and how they compare to various foam toppers (at least in very general terms) in post #8 here and in posts #3 and #6 here and there are some additional comments about wool toppers and a list of some of the better sources I’m aware of in post #3 here but again the only way to know how any combination of materials or components will feel for you will be based on your own careful testing or your own personal experience.
If you let me know your city or zip code I’d certainly be happy to let you know about the better options or possibilities I’m aware of in your area.
You may have seen this already but if you are also considering online options then the mattress shopping tutorial also includes a link to a list of the members here that sell mattresses online and many of them also sell latex and latex hybrid mattresses that use different types and blends of latex that have a wide range of different designs, options, features, return and exchange policies, and prices that that would also be well worth considering.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Phoenix