I am a owner of 2 king size tempurpedic mattress since 2004 and love them. I have found these types of mattresses are very room heat sensitive and there as stiff as a board at 50 degrees. We like to sleep in a cool room, Not 50, and it makes the bed firm. It's also easier to move or roll around without waking up in a hole, like when there hot and you do not get night sweats. I suggest finding the right room tempature for yourself and your bed.
I also have a bad back for the last 24 years, and frequently visit a chiropractor for maintance.

I have owned a king Tempur-pedic with their foundations and mattress sack for almost four years. I am satisfied with the sleeping comfort and can not detect any deterioration in the comfort level. No matter how cool we keep the bedroom air temperature, the area of your body that is touching the mattress retains body heat. Has anyone figured out a solution to this problem?

Do not buy tempur-pedic, I am having a terrible pain in my waist and shoulder after 10 years sleeping in this mattres, The upper level of the mattres after 10 years do not match with the lower level I can't understand how is just out of order.
I sent the warranty papers with pictures many times and I din't receive a response from the company, do not trust in the warranty, nobody from the company will contact you.