The back and arm cushions seem to lose volume...

The back and arm cushions are normally filled with fibre, or feather and fibre, and although they have internal pockets to keep the filling well distributed they can lose some volume with use. To avoid this little problem we recommend you to plump the cushions up regularly.

The easiest way of doing it is taking the cushion with both hands and hitting it (as if you were clapping with the cushion between your hands).