Great Until it Wasn't

We purchased a king Big Fig mattress, box spring, and frame in 2018. Already the integrity of the foam is failing and makes it feel like we're sinking into a hole. On both sides of the bed the sagging is so drastic we're either sliding into it or leaning inclined along it. To say it's uncomfortable is an understatement. It's only been a little over 4 years and we are average size sleepers who rotate the matress regularly, so we were shocked at the speed at which the firmness and comfort deteriorated. With most mattresses lasting 7-10 years, the price of this mattress, and the claims of durability and the mattress' materials preventing sagging, we expected more from Big Fig. We presented these concerns to Big Fig but the warranty only covers if the mattress indents without weight past 1 inch. Our indent was just shy of 1 inch and the warranty doesn't take into account what is happening when you are actually sleeping on the mattress. Be warned. Keep this in mind if you're considering purchasing this mattress. We're regretting our purchase.