Terrible

I purchased this mattress and it was great for about 2 weeks. It literally sags where I sleep and has continually gotten worse. It was replaced once by Mattress Firm (they said it was possibly defective) and the replacement has done the same thing. I have been sleeping on it for 60 days-when I rollover I am literally rolling up hill or down hill. It looks like a hammock where I sleep. Mattress Firm won't do anything because only "1 replacement per order" and now I must file a warranty claim with Beautyrest. I will definitely be filing one, however from what I've read it doesn't sound like I will have any resolution. I had my previous Beautyrest for over 15 years and never had this kind of a problem.