Buying a good mattress is key to a decent night's sleep, but it's not always clear what this involves. Here are five common myths about mattresses demystified. A sagging mattress is the only way to tell if you need a new one If your mattress starts to sag, you definitely need a new one, but it's not the only indication that your mattress is past its best. If you start suffering from aches and pains at night, restless sleep, creaking noises and even snoring, these all could suggest you need a new mattress. As a rough guide, replace your mattress every seven to 10 years. Only ever buy a firm mattress A firm mattress is favourable, but the type you choose should be based on how comfortable and supportive it feels for you, and this can vary from person to person. If you suffer from pressure point pain, you may prefer a medium mattress, for example. The higher the coil count, the better quality the mattress Coil count is worth taking into consideration when buying a new mattress, but it's not the only factor that is indicative of the quality of a mattress. How supportive, comfortable and durable the mattress is defines its quality. I can save money (and the planet) by buying second hand If you value the quality of your sleep and your health, you should never buy a used mattress, no matter how clean it looks. If the mattress has been moulded to the body shape of its previous owner, it might not be suitable for you, and could even contribute to aches and pains. Many new mattresses are incredibly affordable these days, and you don't need to spend a fortune to find one that is both comfortable and supportive. Always buy a mattress with the longest warranty Mattress warranties are often confusing, so make sure you understand the details and read the small print before you buy a new mattress. The length of warranty does not relate to the mattress's life expectancy, nor will it guarantee that the mattress will still be comfortable in a decade's time.