In this study, we calculate the mean lifetime of carbonyl sulfide (COS) and methane (CH₄) in the stratosphere from continuous vertical profiles sampled with balloon-borne instruments. We used two methods based on the stratospheric relationship of these gas species with N₂O. The estimated stratospheric lifetime range is 69–90 years for COS and 146–172 years for CH₄. These results are consistent with other studies and suggest no long-term trends in the stratospheric lifetime of these gas species.