Alternative to current liquid amine technologies for post‐combustion CO2 capture, new technologies such as adsorbent‐based processes are developed wherein material lifetime and degradation is important. Herein a robust method to determine degradation rates in a laboratory setup is developed, which was validated with a continuous multi‐staged fluidized bed pilot plant designed to capture 1 ton CO2 per day. An amine functionalized polystyrene adsorbent showed very good agreement between the experimental 1000‐hour laboratory degradation rates and 2200 hours of degradation in a pilot plant. This validates how laboratory experiments can be extrapolated for sorbent screening and for scale‐up. Resulting, the oxidative degradation in the desorber at high temperatures (120°C) and low O2 concentrations (150 ppmv) is 3 times higher compared to the adsorber at low temperatures and high O2 (56°C, 7 vol%). Laboratory degradation experiments can hence be used to further optimize process operations to limit degradation or screen for potential new adsorbents.