Mattresses tend to last for about ten years before they start sagging. The first time you might notice that your existing mattress is starting to fail is when your back starts to ache or you feel the occasional spring in your side when you turn over.
Given that you can expect to keep your mattress for such a long time before it fails you, though, puts rather a lot of pressure on you to choose the right mattress in the first place. That's not an easy thing to achieve when there is so much choice available. Mattresses are given 'firmness' ratings, normally of between one and seven, but each shop uses different numbers and terms for the level of firmness and ultimately you just have to lie on a lot of mattresses before you find one that feels right. They're all available to go with single beds, double beds, queen beds, king-size beds or super-king-sized beds.
If you can, try to lie on each mattress in the shop for at least five minutes, in several different positions (including the one you most often sleep in) to get a good feel for how well you will be able to sleep in it all night. Some shops offer a forty-night money-back guarantee if the bed doesn't suit you, but that is usually only valid if you buy the bed frame as well as the mattress.
There are several different materials to choose from, too, including memory foam, latex, closed-spring, open-spring, pocket-spring and open-spring with memory foam topper. As if that wasn't enough choice, you can also add a topper to your mattress if you find those ties (that hold the mattress together) uncomfortable to lie on - these can be made from memory foam or feathers. At the more basic end is the foam mattress, which isn't very popular now as it quickly loses shape and support, and if you sleep in the same bed as someone heavier than you, you can both end up squashed together in the dent they create.
A pocket-sprung mattress has an advantage over other spring-based mattresses in that there is minimal movement across the width of the mattress. That means that if your partner shifts position you are far less likely to feel it and stir from your sleep. There is an argument that if you're buying a pocket-sprung mattress you need to choose one that has the most pocket-springs (they are available with anything from 800 to 3,500), but in fact if you buy anything with about 1,000 or more pocket-springs then you will get a comfortable and durable mattress. They're very comfy if you tend to sleep on your side.
Memory foam mattresses are something that you either love or you hate. Once you lay on a memory foam mattress, you can feel yourself sinking slightly as the mattress folds around you, supporting you just where you need it. That is fine if you don't tend to move much during the night, but it is hard to shift position as you have to sort of climb/roll out of your own body's impression in the mattress. If you're on the heavy side, that's no mean feat. They can also feel warm, which is nice in winter but not so good in summer.
Latex mattresses are also an acquired taste. They tend to be more expensive than other types of mattress, and they offer the same sort of support as a memory-foam mattress but with less moulding to worry about climbing out of. Some people report that they feel sweaty after sleeping on a latex mattress. They are a very good buy if you are prone to dust-mite allergies.
Test different types of mattress and get your partner to lie beside you too, so that both of you can choose a mattress that you'll both be comfortable on for many years to come. If you want to know where to buy your next mattress read The Sleeproom customer reviews.