The warranty covers sagging on anything over 2 inches. The cover is for the same duration of each mattresses individual warranty length. Also, any other manufacturer defects.
Mattress Warranties range in between 10-25 years refer to your purchase agreement for the specific length on a particular model. All Mattress America purchases through "More Mattress LLC" must be submitted in writing before the expiration of the warranty. Or by email to email@example.com