Loses support

When new, this was a great bed. After four years, it has lost the support that made it comfortable. The store we purchased it at sent us a warranty check sheet. The sheet explains that the mattress must sag a measured amount before they will repair or replace the mattress. Well, our bed does not "sag" enough to be repaired even though it has lost its ability to support. I purchased this Capital Bedding mattress because of the Capital Bedding spring mattress that lasted me 15 years. A friend of mine that researches product as a part of his job told me that all foam mattresses degrade and will not last through their warranty period. I wish I knew this before buying this last bed.