UM,
If they're eating foam beds then Duvets will just be seen as an interesting alternative (I speak from experience :( ) and the filling can easily be swallowed and cause problems :(
Like you Carene I just give them vetbed pieces now and wash them regularly, although I had to confiscate even those when the pup decided to eat them as well

a week of sleeping on cardboard produced a cure tho :)
for some reason although the pup shreds cardboard it isn't actually eaten ;)