18 months after purchase we are both sleeping in holes

I did a lot of research to find a really good mattress for a change. What is available these days, at any price, has been disappointing. Our last three king mattresses have been at least $2500 each and we have tried Simmons Beautyrest, Sterns and Foster, and Sealy. All were disappointing and lasted a short time, so we got out of the mainstream and gave Charles P Rogers's top of the line Nano a try. Loved it at first. It was on the hard side but had some "give" so was very comfortable. By the end of the first year we knew this mattress was not going to hold up over the long run, despite their claims of using a different type of latex foam that would not collapse and their steel coils that were so much stronger. My husband weighs 230. I weigh 150. We are not exceptionally heavy, but both sides of our king bed are like hammocks. Sometimes I climb onto the mountain between us to sleep and remember how wonderful the mattress was when it was new. We can even see the holes and the middle hump from across the room when the bed is made up. So, I have to say that the mattress was as good as any one I have had in the last 15 years, but it has not held up and I am sorry it did not because for a while it was the best!