Hi Roberto,
Welcome to the Mattress Forum! 
There is also more information about the Dormeo Octaspring mattresses in post #2 here that may be helpful but I would make sure you can confirm the thickness and density of all the layers in the mattress (see this article) before considering it.
There are a few comments about the previous Octaspring 9500 in post #2 here which was somewhat similar but I don’t know the specifics of the current line so you would need to call Dormeo because it’s unlikely that Sleep Country will provide you with the information you need to make an informed choice. It’s also possible that Dormeo may not provide it either.
If you can find out the thickness and density of all the layers and components in the 6700 and post them on the forum I’d be happy let you know if there are any lower quality materials or weak links that would be a reason for concern.
Just in case you haven’t read it yet … I would make sure that you’ve 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 know how and why to avoid the worst ones.
You’ll have to correct me if I’m wrong, but I believe that the mattress ticking is permanent on the 6700, so how would consumers know if the foam in their mattress had tears? I could be wrong here, but I don’t see anything on the Dormeo site about the cover being removable.
Overall, I would be very cautious about using reviews (either positive or negative) as a reliable source of information about either the suitability or the durability of a mattress and in many cases they can be more misleading than helpful because a mattress that would be a good choice for one person may be completely unsuitable for someone else to sleep on (see post #13 here). Instead, focus upon finding out the information I referred to earlier about finding out the actual material and the density used inside of the mattress you’re considering.
If a mattress is well inside the comfort/support range that is suitable for someone and isn’t close to the edge of the range that is too soft for them when it is new and it doesn’t have any weak links in the design 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. But it’s more realistic to think of about 10 years as a maximum reasonable expectation for any mattress no matter what the quality of the materials and then treat any additional time after that as “bonus time” because after about 10 years the limiting factor in the useful life of a mattress will often be the changing needs and preferences of the person sleeping on the mattress and even if a mattress is still in good condition after a decade … a mattress that was suitable for someone 10 years earlier may not be the best “match” any longer.
I would be careful with purchasing and make sure that you are completely familiar with the exchange policy, as the offerings at Sleep Country are brands containing the level of quality of material I tend to advise to avoid, and if you perform an exchange you may be in a situation where your store credit forces you to choose from other lower quality options. The major 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 that 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).
Dormeo hasn’t been on the market for long enough for anyone to be able to really be able to make any meaningful comments about their durability based on actual experience. Outside of PPP (Posture and alignment, Pressure relief, and Personal preferences) … a mattress is only as good as it’s construction and the quality/durability of the materials inside it regardless of the specific mattress or the name of the manufacturer that makes it and there are much more reliable ways to assess the quality/durability of a mattress or know whether it has any weak links in its design than using reviews (see this article and the quality/durability guidelines that it links to). There is also more about the many variables that can affect durability and the useful life of a mattress in post #4 here.
Phoenix