Klaviyo + Postscript SMS for milestone-based winback, what does the 3-month cohort flow look like?

The 3-month cohort is the load-bearing retention pattern for baby DTC. Babies graduate stages every 3 months for the first 2 years; if you don’t graduate them, they churn to the next brand.

The Klaviyo + Postscript flow I ship:

• Birthdate capture, at first purchase (post-checkout survey, “when is your baby due / due-date?”) or via Babylist sync. Stored on the customer entity.
• Stage-graduation emails, fire 14 days before birthdate + 8 weeks (newborn diaper → size 1), birthdate + 4 months (size 1 → size 2 + first foods intro), birthdate + 6 months (size 2 → size 3 + solid foods), birthdate + 12 months (cup / plate / spoon + walking), birthdate + 18 months (potty training intro), birthdate + 24 months (potty training kit + outgrowing diaper sub).
• Postscript SMS winback, 7 days before estimated sub-runout, “running low on size 2? skip-or-confirm” SMS. Converts at ~25%, much higher than email at this signal density.
• Lapsed-buyer reactivation, if a customer hasn’t purchased in 90 days, email “your baby’s probably in size X now, come check out our new size-X bundle.”

Magento webhooks fire to Klaviyo + Postscript on every order, sub event, and address change. Birthdate + stage attribute drive the segment logic. Average impact in my data: 35-55% reduction in 6-month cohort churn vs. brands running generic post-purchase flows.