On 12/16/2006 we purchased two Serta Genesee Top Mattreses from Mattress Warehouse. The sale at the time was ...buy one mattress and get the second one free. We bought the queen size mattress and opted for a single mattress as the free one. A year later, we had the queen mattress replaced because it sagged terribly. It was used on a daily basis. When Bedchek came to measure the queen bed, they found it within their guidelines for replacement. They also measured the single bed but because it is used sporatically, they said it didn't meet their requirements yet. Now that is is used more frequently, it sags in the middle also and will probably need to be replaced. It is very uncomfortable to sleep on.