Great mattress at first, but all goes downhill from there...

Had the mattress for about 3 years now. Coming from a spring mattress, the initial feeling was very comfortable and provided very good support. Did have slight gassing (odor) but that went away within a week. After about a year though, the firmness started to deteriorate. My side of the mattress was much worse than my wife's side as I am heavier than her. We tried rotating the mattress (flipping was not possible as there is only one top side), it helped for a bit, but after 3 years now, the entire bed is saggy. Although there is a warranty, however, it requires the bed to sag without any weight on it. This does not happen, but when there's a person's full weight on it, the bed sags at least another 3-4 inches more than when it was brand new. The bed was purchased with a Groupon deal, so can't complain about the price, but in terms of quality and durability, you are better off spending a little more for a mattress that will last longer.