Hi ohaya,
While I don’t pay much attention to reviews (as you can see in post #13 here) … I looked and didn’t see the reviews you are referring to except one that was written by someone that was over 300 lbs and hurt his back and spent most of his day in bed and in addition to that chose An “8” in firmness level (which would be quite soft for his weight).
All materials will soften and develop some “indentations” over time but it’s really a matter of degree. Latex is the most durable of all the foam materials but there is no material that is soft enough to sleep on that doesn’t soften or impress over time so some degree. This will be more evident with higher weights than with lower weights because higher weights will break down any material faster and with king size mattresses more than smaller sizes because there is a larger area in the middle that isn’t used as much.
When you are in a heavier weight range … then the quality and durability of the materials in your mattress become even more important than they normally would be and the density of the layers immediately below the latex can play a more important role in durability because you will tend to “go through” the top layers more easily. You can read more about the factors that affect the useful life of a mattress in post #4 here. In your weight range I would be leaning towards the Bamboo Bliss with higher density 2.17 lb support foam vs the 1.5 lb version in the Amazon Eurotop and you would also have the cooling benefit of having wool in the quilting of the mattress.
Yes they are except for occasional sales that have a bigger discount than the regular MUG discount.
Phoenix