My Serta mattress started sagging before one year.  After year 2 full body impressions on opposite sides of mattress due to turning mattress.  I bought this mattress for back support as advertised.  I can not sleep in it now due to backache from deep impressions.  I have a 10 year warranty that is why i purchased it.  Serta advised me they will not honor the warranty. It is not sagging enough for them to bother with. I am out for  a king size $1200 and sleepless nights.