Problems with Henredon Cushions

I have 2 sofas from the Henredon Fireside Collection that were delivered Jan 2008. I noticed the cushions not "springing back" to shape after being sat on. The back cushions basically look collapsed. After contacting the dealer in Aug. 2009, Henredon replaced all the cushion cores at no charge. They looked great for a while but the same thing happened again. They have some down in them. I was told I had to shake and fluff them often. They are in our family room and get used daily. Even after they have been fluffed they just squish down again. The fabric moves on the cushion so you have to pull the welts to get it back in proper alignment. I hope this isn't what I should be expecting from these cushions. I have never had to do this on my previous Thomasville sofa.
Help!

A Henredon is a higher level product than Thomasville. You may have had foam cores in the latter, and the down cushions on your Henredon do have to be fluffed the way Linen clothes have to be ironed after washing. There are different levels of down cores, you have pure down and feathers, spring down (Marshall units), down sleeved over foam, etc. If you have pure down and feathers its going to pancake flat every time. Spring down will return to about 85% to 90% after sitting upon and down-sleeved will return to 95%.