You spend about one third of your day” in bed, said Terry Cralle, a registered nurse who also a certified clinical sleep educator and consultant for the American Sleep Apnea Association, a well as director of Business Development for the Woodlands Sleep Evaluation Center in The Woodlands, Texas.

If you’re sleeping on a mattress that’s worn out or needs to be replaced, you could be robbing yourself of restorative, restful sleep.

“Our sleep surface comfort requirements change over time because our bodies change over time,” Cralle said. For instance, a person may need a different mattress as they age or if they have become frail, lost or gained weight, had an injury or surgery or a medical condition such as arthritis.

Mattress Warranties are not an indicator of how long the mattress should be used before it needs replacing, Cralle noted. “The sole purpose of the warranty is to protect the consumer against a defective mattress and materials, not the gradual and inevitable loss of comfort and support.”

Warranties typically are longer than the actual lifespan of a mattress, which averages seven to 10 years. And mattresses that see a lot of use may need to be replaced after five years.

“Even the highest quality mattresses wear out in time,” she said.

Spotting the signs

Unlike a flat tire or a broken window, a worn-out mattress doesn’t always have

obvious signs that indicate it’s time to replace it.

These signals may help you determine whether it’s time to buy a new mattress:

You’re in pain. Waking up with back and or neck pain, numbness, stiffness and aches are telltale signs it’s time to replace your mattress.

You toss and turn. Waking frequently during the night that isn’t related to sleep apnea can be a sign your mattress is preventing your body from relaxing and being able to sleep properly.

You sleep better somewhere else. “If you get a better night’s sleep in a hotel, as an overnight guest somewhere or even on the sofa, your mattress could need replacing,” Cralle said.

There’s a dent in your bed. Any visible sagging spots, indentations or areas on the surface of the mattress that appear or feel uneven mean it’s time to ditch your mattress. “You shouldn’t be able to feel the coils in an innerspring mattress, either,” she said.

A surge in allergy or asthma symptoms. “Mattresses attract allergens, and as the levels of these allergens increase, so does the risk for problems with allergies and asthma,” Cralle noted.

The Better Sleep Council (BSC) suggests keeping these tips in mind when shopping for a new mattress:

Do your homework. Research your mattress size and mattress type options before you head to the store to determine your individual sleep needs.

Test-drive your new mattress. Don’t be shy in the store. Kick your shoes off and lie down on several different models in various positions—including the one or two you typically sleep in. And wear comfortable clothes that allow you to lie down, roll over and move around on the bed.

Be patient. According to the BSC, it can take up to 15 minutes to relax enough to feel the true support of a mattress. Spending a few extra minutes in the store while shopping can spare you from committing to a mattress you don’t love.

Shop around. Mattress are sold at furniture stores, department stores, sleep specialty shops and even discount warehouse stores. The BSC suggests looking for a retailer that has a sales staff knowledgeable about brands, warranties and benefits of the various mattresses.

And make sure to compare prices and features of several brands to ensure you find the mattress that’s just right for your sleeping needs.