Hi Chief,
There are a number of ways to know including …
You wake up in the morning with aches and pains that go away over the course of the day.
You tend to sleep better on other mattresses (friends, hotels etc) or on your couch than you do on your own mattress.
There are obvious signs of foam softening or sagging/impressions that is affecting the performance of your mattress (such as sleeping better in the middle of your mattress).
You don’t sleep as well on your mattress as you did in the first few years.
While some mattresses are much more durable and will maintain their comfort and support much longer than others (depending on the quality and durability of the components) and your own needs and preferences can also change over time depending on different factors such as weight changes, injury, illness, physiological changes associated with aging, and other factors as well … if you are sleeping on a mattress that is 7 - 10 years old or more it would also be a good idea to assess whether you may be better off with a new mattress (using the above criteria). In some cases even a mattress that is only 2 or 3 years old but is made with lower quality materials may need to be replaced because it has lost the comfort and/or support that it had when it was new so I would use your own “best judgement” rather than only the age of the mattress or the length of the warranty (which has very little to do with the useful life of a mattress).
While I’m not a big fan of airbeds for the reasons outlined in this article … if you were sleeping well when the mattress was new and your pain and discomfort is the result of foam softening in your comfort layers it may also be worth considering just replacing the foam in your comfort layers. There are some good sources for different types of foam layers in post #4 here.
You left out the zip code so if you can let me know what it is I’d be happy to let you know about any of the better options or possibilities I’m aware of in your area.
There is more information in the pillow thread here that can help you choose a new pillow that is suitable for your own specific needs and preferences. I would probably choose a mattress first since the type and firmness of a mattress can affect which pillow you will do best with and will keep your head and neck in good alignment in all your sleeping positions.
Phoenix