The bed reached 12 inches within an hour. I didn't sleep on it for 36 hours. The bed had a minor smell when I first opened it, but it disappeared before I slept on it.  I will say this bed leans on the firm side, so I will be getting a topper (which is okay because I was contemplating a 14' before anyway). overall for the price it's a great firm bed. no lumps, no smell, true to height.