As a general rule, bed pillows need to be replaced after 18 months. Memory foam pillows typically last longer, up to three years. Natural pillows tend to be more durable than synthetic pillows. Higher quality pillows are more durable than cheaper ones. If you're using a five- or six-year-old pillow, you're not getting the support you need -- and you're not sleeping very comfortably.
It may seem like a short life, but think about it: your pillow is used about 7-8 hours a night - over 2,500 hours a year! Like your mattress, your pillow is an investment in quality sleep that pays dividends in your waking life.
If you're not sure if there's life in your pillow, you can do some simple tests:
First, remove the pillowcase and examine your pillow. Does it have sweat stains? Is it torn? Does it smell? These are all signs that the pillow needs to be replaced. Pillows collect dead skin cells, mold, mildew, fungi, and dust mites (and their droppings). Over time, half of a pillow's weight can be attributed to these unwelcome microbes, which can trigger allergies, interfere with breathing during sleep, and emit odors that make it difficult to fall asleep.
If your pillow passes the sight and smell tests, it's time to take the fold test:
Fold the pillow in half. If it just folds and lies there instead of springing back to its original shape, it's a dead pillow. With a naturally padded pillow, you can do this test on your arm. Does your pillow dangle and hang over your outstretched arm? That is a pillow that has used up its useful life.
Use a synthetic pillow, fold in half and add some weight to the top - sneakers or shoes work well. Save weight, and if your pillow isn't springing back to its original shape, it's time to replace it.
With a large king-size pillow—whether natural or synthetic—you'll want to fold in thirds, not halves.