It's important to assess your ergonomic chair periodically to ensure it provides optimal support and comfort. Generally, you should consider replacing your chair every 5-7 years or when you notice significant wear and tear on the materials, such as cushion flattening or compromised adjustability features. However, the actual replacement timeline may vary depending on the quality of your chair and how heavily it is used daily. To maintain good ergonomics, make sure to regularly inspect your chair for any signs of damage or reduced functionality and replace it when necessary to avoid exacerbating existing health issues like lower back pain or sciatica.