Often the most comfortable seat in the house is the one that gets the most traffic and attention. For some, this might be the couch; for others, an armchair. After years of use, the cushions are often half the size they were when you bought the furniture. While punching the cushions is a quick fix, there is a more strategic way to get the cushions to revert to their plumper state. In the end, you'll feel like you have a new piece of furniture.
Place an old, clean dark sheet on some grass in an area of full sunlight on a very sunny day. Arrange all your cushions on the sheet. The dark colour will help attract more sun to the cushions.
Space the cushions with several inches between each one. Leave them in the sun for around four hours, no longer. Leaving them in the sun longer could fade their colours. Take the cushions back inside; they should all be significantly plumper as the sun dries out the excess moisture within the cushion, making it fatter because moisture plays a role in flattening it.
Hold a cushion by adjacent corners. Bring your hands together so the corners meet and then yank the corners straight out. Do this in one swift movement. Rotate the cushion so that you do this again with the next side. Repeat until the cushion has made one full rotation.