Hi Ritz.
Welcome to our Mattress Forum 
Good to see you have done some research and narrowed your mattress options to the Cocoon Essential and Springwall Campus mattresses. I am sorry to hear you have started experiencing back pain with your current mattress. Sagging and virtual impressions are the common reasons why people start getting gradually out of alignment and experiencing back pains. It’s very likely that your mattress is lacking the support needed to keep your spine in neutral alignment.
Canada Sealy also does not disclose any meaningful information about their mattress layers. I looked around for some more info on the (8") Cocoon Essential specifications including the foam thickness and density but had no more luck than I did in the pas to find the specifications you’d need to know to make an informed purchase. We did have a few consumers that managed to find out specs of the (10") Cocoon Classic which had some weak links on the foam quality/durability side.
Typically major mattress brands like Sealy are among the least transparent in the industry and they tend to use lower-quality materials in their mattresses than most of their smaller competitors … 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 linked below along with some simple Q &A in Post #3 and Post #12 about Major Mattress Brands and some more “buzz” about marketing stories & major mattress brands) .
If you are considering this mattress, I’d keep in mind that the Essential is the Medium option of the Classic that comes in Firm and soft.
Springwall is a Canadian independent manufacturer of higher quality mattresses. I’d still want to find the foam densities as this line up is made to requirements exclusively for Costco and Costco website does not list anything other than very basic information for Campus 8". You may wish to contact Costco directly or Springwall manufacturer to see if they are willing to tell you the density of the foams they are using: (Phone: 905-564-5008 Email: [email protected])
This is what Costco Canada lists on their website for Springwell ~ Campus 8" Mattress:
• 5.1 cm (2 in.) ViscoGel memory foam
• 15.2 cm (6 in.) high-density bio-foam core
Without knowing the specifications that would allow assessing the quality of this mattress you or I won’t be able to tell how long or if it would last around 5-8 years. This is the part of your research that you can’t see or “feel” and assessing the quality/durability and useful life of a mattress depends on knowing the specifics of its construction and the type and quality of the materials inside it regardless of the name of the manufacturer on the label (or how a mattress feels in a showroom or when it is relatively new). With this or any new mattress you are considering I would always start with …finding out the information listed here so you can compare the materials and components to the quality/durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before deciding if it is actually suitable to you.
In terms of suitability also, I can’t speak to how any mattress will “feel” for someone else because this is too subjective and relative to different body types, sleeping positions, and individual preferences, sensitivities, and circumstances … outside of PPP(Pressure relief, Posture & alignment, and Personal Preferences)
If you can find out or confirm the foam density for all the layers in both mattresses (either from your retailer or from manufacturers) and post them on the forum I’d be happy to let you know if there are any lower quality materials that would be a cause for concern or that would compromise the durability or useful life of either mattress.
Wishing you the best of luck in your mattress shopping journey!
Phoenix