Hi chamcham,
Welcome to our Forum all the way from Northern Ireland!! 
Thank you for sharing your stats and sleep history. It’s a pity you didn’t discover The Mattress Underground a decade ago when you first started your mattress quest. I’m sorry to hear about the pains you’ve experienced and the issues with dips and sagging in your previous mattresses. On the bright side, you didn’t spend too much on those three mattresses, and you’ve gained valuable experience along the way. It seems you’re better equipped for this search!
As you’ve observed, aside from Posture and Alignment, Pressure Relief, and Personal Preferences (PPP), the durability of a mattress is crucial. It’s something you can’t fully assess in a showroom or with a brand-new mattress. To assess durability, you’ll need to know the type and quality of materials inside and the specifics of its construction, regardless of the name of the manufacturer on the label.
In general, I’d start by finding out Mattress Specifications you need to know .for each mattress you are considering Compare these specs against the mattress durability guidelines here to make sure there are no lower-quality materials or potential weak links that might affect longevity. If a mattress doesn’t provide this information, it might be best to cross it off your list.
It sounds like you’re experiencing a classic case of “mattress sag and pillow mismatch.” Before we launched TMU, I suffered from severe lower back pain due to a national brand pillowtop mattress that had developed significant sagging over three years—sagging that wasn’t visible to the naked eye. Interestingly, the pain would subside as the day went on, which made me suspect the mattress was the culprit. This quest to find a solution for avoiding sagging mattresses was the driving force behind starting TMU.
In your situation, the pain and discomfort in your upper back, shoulders, and neck is likely due to a combination of a failing mattress and an unsuitable pillow. Before you invest in a new mattress, you might find relief by adjusting your current pillow.
A pillow that maintains neutral spinal alignment and doesn’t force your neck into an awkward lateral position (for side sleeping) could make a significant difference. You may want to consider a pillow with adjustable filling, like a shredded latex model with a zip cover, which allows you to customize the pillow’s height to better suit your needs. This flexibility also means you can tweak the height as you transition to a new mattress. A memory foam pillow can create allergic reactions in some people and are notorious for the temperature build-up and sinking-in issues you mentioned.
For side sleeping, factors such as your somatotype, muscle build, and arm positioning are crucial in choosing the right pillow. If you place your arm outward and flex your shoulder joint under your head, the pillow’s thickness and firmness might need adjustment. Similarly, if you tuck your hand under your cheek or adjust your arm’s position, this will affect your pillow needs. Pain in the upper back for back sleeping could be due to a pillow that’s too thick, causing your head to jut forward, much like the posture from hunching over a computer for too long.
Generally adjusting your pillow to better support your alignment can be a game-changer.
In terms of the mattresses on your finalists list.
“What” to choose in terms of either a mattress or the balance between comfort/pressure relief and support/alignment that may be suitable for a specific person is always up to the only person who can feel what you feel on a mattress and best left to personal testing and your own experiences or more detailed discussions with the more knowledgeable people at the retailers or manufacturers that sell a mattress you are considering.
This said, here is some food for thought that may help
The Relyon Luxury Silk 2850 has a much lower price point pocket springs mattress with a micro coil layer in the pillowtop. The mattress seems to be well constructed using good quality materials with no weak links or reasons for concerns for your normal BMI range, if you like the feel of the micro coil layer.
I haven’t tried a Relyon but I have Vispring fresh in my memory after testing several mattresses at the Las Vegas Market about a week ago.
Vispring certainly makes some exceptionally high-quality hand-built and tufted mattresses that use high-quality materials and components (pocket coils and natural fibers) but as you know they are in a much more premium budget range than many other mattresses that also use natural materials. There are certainly cases where a mattress in this budget range may be “worth it” for a particular person that isn’t price sensitive and that has specific criteria that aren’t available in lower budget ranges.
With that being said… I should also mention that the most knowledgeable people I have talked with about “super-premium” brands (including some who have worked at some of them or toured their factories) have always spoken highly of ViSpring and tend to rate them either among the best or often the best of the super-premium fiber/innerspring brands.
In many cases, innerspring/fiber mattresses are on the firm side, particularly as the fibers compress, but it’s unlikely that you’d develop “dipping and sagging” with ViSpring or Hypnos due to the natural fibers used in their mattresses. on two counts:
as you noticed with your memory foam temperature issues and possible allergies that may have developed due to the petroleum-based foams and chemical flame retardants that emit harmful off-gassing that are utilized in most lower-end mattresses. Truly organic and all-natural mattresses are free of these ingredients and have many other benefits such as being hypoallergenic, durable, and very comfortable (once you find the right comfort choice for you) Generally natural materials last longer than synthetic ones. Therefore, with a reputable mattress company you are looking at a long-term investment… the expected life span of an all-natural or organic mattress is ten years with the best brands offering 20-year warranties. The lower-end mattresses generally have a 6–8-year lifespan, no matter what their warranty terms would say (especially the small print) One other advantage of these types of materials is that they require very little if any maintenance at all. The vast majority of organic mattresses do not require you to flip or rotate them.
ViSpring is manufacturing their own mattresses in the UK and Vanadium pocket coil springs in their workshop in Plymouth. They have been around since 1901 and over time have developed a strong reputation of maintaining their production standards.
Both Vispring and Hypnos are very well made and don’t have any lower quality materials or weak links in their design so I would treat them as equivalent in terms of durability and I would choose between them based on which of the two your careful testing indicates would be the best “match” for your body type, sleeping positions, preferences and sensitivities and all the other parts of your personal value equation that are most important to you.
JJPierson in Craigavon does carry the Devonshire and currently has a sale, but it does not seem to have the firmness customization options. John A Shannon in Kilkeel seems to offer customer premium support so you may want to call them and ask about firmness customization options and suitability for you.
It’s worth mentioning that Vispring Vanadium steel pocket coils come in about 75 distinct spring types/tensions and their staff is very skilled in being able to tailor the spring tension to fit the sleeper needs. Most of their vendors have sales consultants with sufficient knowledge and expertise to guide consumers. But you should be able to follow the weight guide advice from their website or contact them directly Email: [email protected] | Phone: +44 1752 366311 .
In the case of Vispring their Comfort Promise and 30 year Guarantee it’s well worth having. They stand behind their products and have well-defined policies. The same goes for the other super-premium manufacturers you mentioned. If you decide to go with Vispring, their warranty is important not necessarily because of possible durability issues but for their “comfort promise” if your comfort firmness selection is inadequate or for imperfections, defects in materials, or workmanship. From what I read on their site the Vispring “guarantee only applies to mattresses or/and divans, purchased from an authorized retailer and which remain in the country of purchase” If you buy the product from a retailer in Ireland you should be able to make a warranty claim or to use their comfort promise. I’d call each individual vendor and ask about it.
Hopefully the “feeling desperate” turns into a happy mattress hunting, so let us know if you need any more advice!