I stand by my post of sleeping better!!  My two cents though.  I am convinced after getting down to almost just springs and latex, that the dip will never quite go away.  After sleeping on one side of the bed for a few nights, I can tell it's flattening a little.  I try the other and it is always higher and "firmer".  I think it must be the nature of latex and or foam to require inhaling air after use.  It must take a couple to few days to do so.  Because when I give one side a break for 3 days, and then go back to it, after "wearing down" the other, it's back to normal.  It seems to be a side to side thing, not just one big dip in the middle.  Either that or not only is foam cheaper these days, but springs are too.  I am 135lbs.  I don't think I am overwhelming the foam. 

Any thoughts???????

Latex should spring back to the original shape immediately.  Other foams may take a while.

Maybe your memory foam is worn out (or was it a new one?) or the poly layer underneath?  Yes, it could be the springs ain't what they use to manufacture.  Remember they use to make the edges with steel or whatever, not the foam or plastic they use now.  Nothing seems to be the good quality they use to make, have you noticed?