Hi Pileot and welcome to the Mattress Underground 
I need help finding a replacement mattress. My last mattress was a Kingsdown Loyola and when it was new it was fantastic. After about half a year however it became TOO soft and a little saggy, especially in the middle
Not too surprising; Kingstown , like many of the ‘big brands’ is not very transparent on their materials, or density if they’re components. The Loyola is a 15" latex and gel memory foam hybrid with tri-zoned encased coil support. While Latex is a good and durable material, there is no information on the thickness or density of the latex or gel memory foam, that may affect durability which is very important as you are larger BMI sleepers. While the coil count or gauge for their innerspring is not as important all the missing specs combined, making it hard to assess how it would hold I up for any sleep profile. As larger sleepers, I suggest you avoid any mattress which does not have that info available. As you’ve seen, they may me great initially, but prematurely wear down which causing areas of ‘ridges’ and ‘valleys’ in the memory foam as well as sagging which can cause all sorts of muscle and joint pain and can even lead to alignment issues. Especially frustrating with the warranty terms you describe, which would prevent consumers from returning anything but the most defective prematurely worn products.
I am 6 feet tall, 240lbs and sleep on my side / back. My partner is about 5 feet tall and also around 240 lbs and generally sleeps on her side. We are not light people and we like to cuddle so we need something that will support our weights but also be soft enough that spooning won’t cause our sholders or arms to go numb.
What should we do?!? We’ve looked into other latex mattresses but they are rather expensive and we can’t afford to spend that kind of money if the mattress will wear out in a year. We’ve considered a box mattress, if it’s cheap and we don’t like it at least it was cheap right?
Any mattress you choose will be unique to you both, based on your Stats (height, BMI, sleeping position(s) and any underlying health concerns) and your PPP (Posture and alignment, Pressure relief, and Personal preferences). With your larger BMI’s Id definitely checkout the Mattress Specifications You Need To Know and compare them to the Mattress Durability Guidelines to see how specific materials hold up over time; latex is one if the most durable materials you can have in a mattress, and a well made latex mattress should be far lass pricey then the Kingstown and should last for many many years IFD you find the right comfort and support combo and provided that you don’t choose a too soft latex layer on top.
As you both seem to be gravitating toward a latex hybrid, and are also looking for lower price points for the same quality and comfort, I’d definitely have a look at the many of the Trusted Members of the site offer a variety of latex and latex hybrids, like Arizona Premium Mattress, SleepEZ, Flexus Comfort, BioSleep Concept, Luma Sleep and Custom Sleep Technology…by providing any of these with some info like your Stats, PPP and mattress history, they can help guide you to a quality sleep solution within your budget range. If you find any specific mattresses you have questions on, please feel free to post them and we can possibly comment on how they may be compatible for you.
~ Basilio