Couch cushions are susceptible to going flat as we place them under significant pressure and wear-and-tear on a daily basis. This can compress the foam over time, leading to flat and uncomfortable couch cushions. As this is completely normal, it is hard to avoid it completely, but it should only happen after a few years of owning your sofa. Any sooner and you should check your couch's warranty to see if you are entitled to a replacement cushion.