This document discusses how to analyze and monitor the health of a customer base using cohort analysis. It makes three key points:
1. Always "equalize" customers by capping cohort comparisons at a set age to avoid false alarms from older cohorts having more lifetime value.
2. Use "milestones reached" metrics like percentage reaching a second order or discount rate to track cohort behavior better than average metrics.
3. Monitor the active customer base size and response rather than total customers to remove the effects of churned and new customers which can obscure the picture. The focus should be on the customer segments that are most important to the business.