You want a mattress that provides head-to-toe comfort, while also keeping your body properly aligned, fully supported and at a comfortable temperature. And that’s just for starters. You also need to be able to sleep deeply, through anything – because last night, a dog was barking at invisible squirrels, and tonight, your noisy neighbors are having a late-night party – and tomorrow night, who knows? It can take up to 24 hours for your mattress to fully expand and reach its full potential. It’s totally fine to sleep on it whenever you want to, though.