I had been debating for a long time whether to order a memory foam mattress and after lots of research, I decided on a queen sized from Zinus based on high number of solid reviews (at the time 11,000+ reviews at 4.5 stars) and the cost. I debated on the 10 inch or 12 inch since it was only a $40 difference but ended up going for the 12 inch.
The mattress came in a huge box within 2 days of placing my order. Just another reason why I love Amazon Prime--the convenience of delivery when you live on the 2nd floor is incredible! We immediately opened it up and placed it on the slats of the bed frame. It slowly unraveled and immediately began to expand. No fuss at all with getting it together.
I read that it could take a few days for the mattress to expand to its full height as long as its not disturbed. By the end of the first night, it had reached about 9 inches. By the next day it had expanded to 10 inches. But unfortunately after a full 5 days of being undisturbed (did not lay on it, kept the pup off of it and did not place any sheets or bedding over it) it did not expand any further. I had read some of the comments left by other purchasers and knew that this could happen so after day 6, I had my first night of sleep on it. It was incredibly comfortable and unlike others, I did not find it too firm at all. There is a chemical smell but after a few days and some Febreeze, it went away.
I am very happy with the mattress thus far. It really is super cozy to lay on---exponentially more than my previous mattress that was much pricier. I'm only disappointed that it did not expand to the full height as I had ordered. I'm glad I ended up ordering the 12 inch versus the 10 inch because the latter could have potentially only expanded to 8 inches. It was difficult to find the company's contact information but I contacted Amazon regarding the issue and they refunded me the difference in cost because there was no way we'd be able to return it. I suggest that if you're really set on a specific height of mattress, order 2 inches up.