It's been about a little less than 5 years and we are replacing this mattress. It has lost firmness/strength quite quickly and I feel painful if I sleep on it without 3 inch topper. I actually have been using it with topper for last 2 years. On comparison I still have a queen size foam mattress in the master bedroom which is still standing strong (though it also did become a bit softer overtime) after 8 years.

It maybe okay mattress but you might want to have topper on it to increase its longevity. It was okay during first two years or so but lost strength just too quickly. I had expected it to go through couple more years.