The current trend seems to be to encourage consumers to believe that high quality mattresses last about 8 – 10 years and lower quality mattresses last shorter times before they need to be replaced.
This answer ignores the size, weight, physical effects of aging and other characteristics of the person (or people) using the mattress.
This simple question has been hotly debated within the mattress industry for the past 60 years. The answer changes periodically.
Over the past half century various brand name mattress manufacturers and industry “councils” have experimented with various warranties.
They have tried 10 year, 15 year, 20 year and 25 year warranty recommendations for their top of the line mattresses — trying to find the perfect balance between perceptions of quality and encouraging obsolescence.
The mattress industry’s answers to the question of when to buy a new mattress are primarily related to marketing.
As far as I know there have never been any conclusive scientific studies on the topic that account for the type of mattress studied and the size and physical characteristics of the person using that mattress.
Typically brand name mattress manufacturers try to encourage low warranty periods so that consumers will purchase their products more frequently.
On the other hand generic and less well-known brands often encourage higher warranty periods as that gives their products the appearance of higher quality.
Customers in mattress stores typically face the same dilemma. Which is better? — The name brand mattress with the 10 year warranty? Or the store brand mattress at the same price that features a 20 year warranty? (Typically there is a lower markup on brand name mattresses.)
Warranty periods for brand name mattresses that are advertised nationally (Sealy Posturepedic, Serta Perfect Sleeper, Simmons Beautyrest and several others) are determined by the mattress manufacturers.
Warranties for lower quality mattresses or non-brand name mattresses may be determined by the retail store buyers.
In the end there is really no set amount of time when a mattress should be replaced.
Mattresses may be fine structurally for 20 years or more, but that is not the only factor to be considered.
It is almost impossible to tell whether a mattress is right for an individual after a few minutes of testing in a mattress store or even after a few weeks in your home.
Even if you have been lucky enough to find the “perfect” mattress it may not be as comfortable 5 or 10 years down the road after you have gained 20 lbs. or found a partner to share the bed with.
Basically, the question of how often you should buy a new mattress is best answered, “Whenever you feel that you are not getting a good night’s sleep and that the problem can be corrected with a different mattress.”