had an old mattress and finally decided to replace it with. 
It arrived quickly and folded in a box. It started expanding immediately once out of the box. Instructions said to let it sit for 24-48 hours. I slept on it after 24 hours. It had a strange odor and was very firm. I was a little worried that it was too firm and maybe should have waited the 48 hours. 
I did put my down mattress cover on it.  It took a couple of days for the odor to disappear. It took 2-3 nights of sleeping on it to adjust. 
The mattress is actually very comfortable. I’ve had it for about 3 weeks and am enjoying it so far. I’m glad it made the leap to get a new one.