I'm a decluttering expert. Here's how to know when to replace your pillows, mattress, and sheets.

The less time bedding spends touching your body, the longer it lasts. Pillowcases should be replaced every three to five years, comforters every 15.

• I'm a professional declutterer and work with clients on getting rid of things they don't need. 
• The more time bedding spends in contact with your body, the sooner you need to replace it. 
• Pillowcases last three to five years, while comforters last 15 years or more. 

As a professional declutterer, I know there are some items in the house that beg to be replaced, and then there are those you don't think about all that often.

When was the last time you really looked at your sheets or comforter? You use them every day, but you may have failed to notice that your linens could be past their prime.

Spring cleaning season is over, but it's never a bad time to examine your bedding and swap out the stuff that's worn out or uncomfortable. Some bedding lasts longer than others. Rule of thumb: the less time it spends next to your body, the longer it will last. Why? Well, because we're humans, and we're kinda filthy, even when we shower daily.

You should change pillowcases more often

Sheets and pillowcases can enjoy a nice long life, depending on their materials and the amount of use they get. Not surprisingly, the cheaper they were to begin with, the more often you'll have to replace them. On average, they should last you three to five years. If you've got multiple sets and rotate them regularly, you can hold on to them longer.

Once they're pilling, stained, or threadbare, they're done. Your tolerance may vary, but be nice to yourself. Buy the best quality you can and replace them as soon as you no longer sigh with pleasure when you slip into them at the end of the day.

Pillows should be washed often

You're used to washing your sheets and pillowcases weekly, but you may be forgetting about the pillows themselves. Pillowcases will protect them to some extent, but you should really be laundering your pillows every six months or so.

It turns out this is pretty easy; most can be tossed in the washing machine. But read the care instructions — you don't want to mess up your pillows or your washer. The adage that you get what you pay for is generally true. If you're springing for high-quality feather pillows you can keep them for decades, provided you're cleaning and fluffing them regularly.

If you prefer polyfill, cotton, or foam, you'll need to swap those out more frequently. Replace them every two to three years, but the real test is how they feel. Once you notice clumping or lumpiness, it's time to go shopping.

Mattresses and comforters last longer

Common wisdom is that a mattress lasts about 10 years. If you opt for something super fancy (and expensive), you may get more mileage out of it, but once you start to notice any sagging, it's time to get a new one. Don't put this off; your joints and back may never forgive you. Options abound when it comes to materials, and it's easier than ever to get a good mattress for not a lot of money.

Comforters are the real workhorses of the bed linens. They should last from 15 to 25 years, provided you're keeping yours in a duvet cover that's washed regularly. Since comforters are lying on you, rather than the other way around, they can maintain their shape and loft for ages. Wash it once or twice a year according to the manufacturer's instructions, and store it in a dry, non-musty cupboard when you're not using it.

Here's the real deal: once any aspect of your bedding starts to feel less than dreamily comfortable, it's probably time to replace it. Americans are already short on rest. A recent Gallup poll indicates that fewer than half of us feel we're getting enough sleep. The numbers bear this out; over the past century the national average of hours we're snoozing each night has dropped precipitously. Obviously, bedding isn't to blame, but why not create the coziest nest possible?

Once you've decided to replace your sheets or pillows, get the old ones out of the house. You cannot save them "just in case." You are allowed to turn sheets into drop cloths or tear them up for cleaning rags, but once they've passed their prime, get rid of them. You deserve nice things.