Grouping customers by when they first bought, then tracking how each group behaves over time, repeat rate, revenue, retention. Cohort analysis is how you see whether the business is actually getting healthier or just bigger: blended averages hide the trend, cohorts expose it. If newer cohorts retain worse than older ones, you have a problem that growth will only amplify.
Benchmark. Look for repeat purchase rate and cumulative LTV climbing across successive cohorts. Flat or declining cohorts mean you are buying growth that does not compound.