Hi luxastraea,
You can see some comments about Dynasty in posts #3 and #4 here and a forum search on Dynasty (you can just click the link) will bring up more comments and information about them as well. I would also want to know the density of the two convoluted layers underneath the memory foam as well because convoluted layers can be less durable than solid layers of the same material (see post #2 here)
I would also keep in mind that there is always some additional risk and uncertainty involved in buying a mattress that is made in China or other imported mattresses that may be subject to longer periods of compression during shipping and storage that can sometimes affect the durability and useful life of the mattress (see post #6 here).
I would also put much more emphasis on the return policy of an online purchase (and the costs involved) so that you can decide on whether a mattress is a good “match” for you and how well you sleep on it based on your own experience rather than using other people’s experience that may be very different from your own.
Phoenix