Given that we spend about one-third of our lives sleeping, you'd think we'd spend a little more time choosing and caring for our pillows. But too often we buy them without deliberation, care for them not at all and use them way beyond their age of retirement.

If your neck is sore and stiff in the morning, if in the middle of the night you sometimes notice that your arms are numb or if you're just not feeling well rested, you probably need a new pillow. Here are some things to consider:

The purpose of a pillow is twofold: to provide comfort and to keep your neck and spine aligned while you sleep.

As a rule, extra-firm pillows are best for those who sleep on their side. Side sleepers should make sure the height of the pillow is roughly the same as the length of their shoulders (the distance between the base of the neck and the end of the shoulder).

Medium-to-firm pillows are best for back sleepers. These provide support without tilting your head too far forward or allowing it to tilt too far back.

Medium-to-soft pillows are best for stomach sleepers. The risk for stomach sleepers is that your head will be pushed up and back while you sleep, putting stress on your neck and spine. Be sure your pillow keeps it all in line.

Natural-fill pillows, such as down-filled, are typically more expensive than most synthetic fill pillows. Upside: They tend to last longer. Downside: They tend to be softer, and many allergy sufferers cannot use them.

Not all pillows made of synthetic materials are inexpensive. Pillows made of space-age foam can cost $70 or more. Upside: These pillows provide maximum support and will not break down as quickly. Downside: the cost.

Pillow protectors are important in preserving and prolonging the use of your pillow. These are not the same as pillowcases that come with sheets. These are covers you zip on over the pillow that protect the pillow from perspiration, stains, dust and allergens. Pillow protectors also increase comfort. Wash your pillow protector every time you wash your sheets.

Your pillow is not your friend. It's only a sleep aid. Loyalty and emotional attachment to a pillow is not healthy. At some point it will need to be replaced. You wouldn't keep wearing a pair of shoes that were worn out and made your feet sore and tired, would you?

Fluff your pillow regularly. This incorporates fresh air into the pillow and helps maintain its shape.

Clean your pillow regularly. Read and follow the manufacturer's care instructions.

Most synthetic fill pillows can be machine-washed. Down pillows should be dry-cleaned. If the instructions say that machine-drying is recommended, dry it on a low setting until completely dry. To enhance fluffiness, dry it with a clean tennis ball.

Sources: Gigi Jensen at www.hgtv.com, www.bedbath andbeyond.com