This mattress (icomfort Insight) was our first memory foam mattress purchased March 15, 2013. For the first few years, I had the best nights sleep of my life: no waking in the middle of the night, no lower back pain. We are now on year 4 and I am sleeping on the couch. The mattress has sagged and there are two dents where we sleep and a hump in the middle. I wake up several times during the night and the sagging has brought lower back pain. Since it is memory foam, I can't see the dents but can feel them. We are not heavy people either. My husband is 185 and I am 133. I am so disappointed in the longevity of this mattress, especially since I loved it so much in the beginning.