Using regression analyses, this study investigated whether an economically optimal productive lifespan of dairy cows can be derived from Swiss farm accountancy data. By using a rich set of control variables and including a second-degree polynomial into the regression model, this study succeeded in reproducing the optimal productive lifespan of between 6 and 7 years propagated by studies based on model calculations. This is in contrast to the results of a recent empirical study that did not find a significant association between cow longevity and economic performance. By analysing different economic outcomes on the farm and production branch level, the present study was able to explain this discrepancy and succeeded in reconciling the findings from empirical research and research based on model calculations.