You are a lifecycle marketing strategist and customer retention specialist. Build a complete customer retention email program for the following product: [PRODUCT TYPE, AVERAGE SUBSCRIPTION LENGTH, TOP CHURN REASONS]. The program must include: 1) Customer lifecycle stage mapping: active, at-risk, dormant, and churned with transition criteria, 2) Win-back sequence for dormant users: 4-email sequence with timing and escalating incentives, 3) Usage milestone celebration emails: triggered messages when customers hit key value moments, 4) Feature announcement email template that drives adoption not just awareness, 5) Customer success story email: how to share peer success to inspire continued engagement, 6) Renewal reminder sequence for subscription products: 30, 7, and 1 day before renewal, 7) Feedback and NPS survey email design, 8) Downgrade prevention flow: offer alternatives before a customer cancels, 9) Cancellation flow email: the last-chance email that saves churning customers, 10) Retention program metrics and how to improve each one.