Hi there -- Thanks for your question. In general, you can continue to use a mattress as long as it continues to meet your requirements in terms of the 3 F's (https://www.goodbed.com/guides/mattress-matching/). Most critical is that you are continuing to receive proper spinal alignment and adequate pressure relief. So in terms of whether you should be replacing your mattress, you are in a far better position to assess that than anyone else.

In terms of how long that particular model would ordinarily be expected to last, I will take that two ways. First, air chambers tend to be very unique amongst mattress support types in terms of their rather binary wear profile -- meaning that in general, they either work or they don't. As long as the air chamber continues to hold air, it should be just as supportive now as it was when you bought it. But on the flip side, an air chamber is far more prone to catastrophic failure (eg, popping) than any other type of mattress. And of course, there is also a noteworthy gray area where it develops a slow leak, forcing you to constantly refill it, which is annoying at best, and more likely will mean that its end of life is imminent.

Beyond the air chamber, an air mattress also has layers of foam above the chamber, which is what provides the comfort and pressure relief. These will be at least as prone to break down as the upper foam layers in any other mattress. I say "at least" because the air chamber itself provides less give than a typical support layer (at least when it's a single-zone air chamber like you'll find in this Sleep Number model). So while other mattress types can distribute their wear across both the comfort and support layers, this type of air mattress concentrates all of the stress on its comfort layers, which can lead those layers to degrade sooner. You can think of this as the flip side of the longevity benefit described in the paragraph above, since the benefit of an air chamber that doesn't absorb wear comes with the cost of imposing all that wear on the materials above it. If you sleep on your back, this might not be a huge issue, but if you sleep on your stomach or side you will will most likely notice this at some point.

In terms of the specific materials used in the Sleep Number 5000, I'm afraid we never did an in-depth review of this model, so I can't offer much more detail on how those particular foams are likely to hold up relative to other foams. Nonetheless, I hope that general information above gives you a sense of what to look for and how to decide whether it's time to replace your mattress.