My husband and I purchased our King Size Serta mattress (and box springs) about 18 months ago and we are now looking to purchase a Sleep Number bed. After 6 months we noticed the bed was begining to sag where we slept (I'm 5'6", 150 lbs & my husband is 6'0", 200 lbs). With neither of us being particularly "large people" we thought this to be poor manufacturing - indeed, it is! We now have a 1-2" sag on each side of the enormous hump that has arisen in our mattress an no warranty to fall back on because Serta doesn't stand behind their products.

Be warned that any mattress can have it's downfalls...