We show that group sequential designs (which allow to perform interim analyses while data collection is ongoing) can unlock numerous benefits for researchers engaged in confirmatory hypothesis testing: They facilitate sample size decisions, allow researchers to achieve a desired level of statistical power with a smaller number of observations, and help conduct more efficient pilot studies. We validate this cost-saving potential through a comprehensive re-analysis of 212 studies published in the Journal of Consumer Research, which shows that using these designs would have reduced costs by 20% to 29%. We conclude with a discussion of limitations and possible alternatives.