Update:
We have had this mattress just over 3 years and it is becoming increasingly more uncomfortable.
There are deep depressions on both sides of the mattress. We have been rotating the mattress every 6 months.
 
I cant say enough about this mattress. I researched mattresses before I purchased one. I like the fact the foam is (CertiPUR-US Certified) so I we can rest easy knowing it is safe from VOC's. This is the most comfortable mattress I have ever owned, we just love it.