I bought this mattress just over 2 years ago.  At first it was good; but now it does not hold up.  I have 2 dents on either side.  The mattress can not be flipped over, only rotated.  It is so heavy makes it hard to do on your own.  I now sleep in the middle of bed to try to even it out.  I am shocked how the reviews seem so good.  I am not a heavy person either - 5'8" at 140lbs.   My back bothers me all the time.  Not a good bed for someone with back issues.