1. Comfort: Has sitting comfortably in your chair for long periods of time become increasingly more difficult? This is a sign that your chair is not providing you with enough support. Finding a new, ergonomic chair will help to fend off a hurting back and strained neck.
2. Condition: Another simple way to see if your chair is ready to be replaced is check the condition of the chair's mesh and foam. The chair is likely no longer safe to use if the mesh, foam, or hardware are worn out or broken. Take a look to see if these aging parts could be a hazard.
3. Cost: If you have been using an inexpensive office chair for years, it probably needs to be replaced. Even if your inexpensive office chair does not appear to be falling apart, it is very likely that it is not providing the support that you need. Consider making an investment in buying a highly supportive, well-made ergonomic chair like the Herman Miller Aeron. You are sure to get full value out of a well-made chair, as it will provide the best back support possible and will last for years.