How companies actually engineer retention
Behavioural autopsies of real products — Notion, Kit, Chowdeck, Glovo, Risevest. Real email captures, trigger logic mapped, and what you can take from their architecture.
A letter · on the post-signup revenue layer
The Perennus Letter.
Lifecycle intelligence for operators who take retention seriously.
Teardowns of real lifecycle systems, automation architectures you can steal, and operator-level findings you can’t Google. It goes out when there is something worth sending. Free.
SubscribeFree. Unsubscribe anytime.
What I write about
Not tips. Not hacks. Infrastructure-level thinking.
Every edition is built for people who run the post-signup revenue layer — the part of the funnel most teams build once and then never watch.
Blueprints you can steal
Trigger logic patterns, data property design, scan frameworks. The infrastructure behind always-on lifecycle systems — laid out so you can rebuild it yourself.
What broke, what we fixed, the math
Anonymised findings from real scans and consulting engagements. What the leak was, what it was costing, and how it was fixed — with the revenue math attached.
Recent editions
Four letters, most recent first.
Read any of them before you decide whether to subscribe. Nothing here is gated.
- 28 July 2026Your Customer Cancels Long Before They Click “Cancel.”Why healthy retention systems monitor changing behavior—not disappearing users.3 min read
- 14 July 2026Your ESP Says “Delivered.” Gmail DisagreesThe deliverability metric that quietly convinces growth teams everything is fine3 min read
- 7 July 2026Your onboarding emails are running on a calendar. Your users aren’t.Why treating every user the same is quietly hurting activation and retention.3 min read
Earlier letters — from before this became a lifecycle publication — are still up. Full archive ↗
When you subscribe
You also get a free 3-day email course.
Before the letter starts arriving, you’ll get a focused course on the retention truths most subscription businesses never see.
Day 1
Why blended LTV:CAC hides cohort-level bleeding
The number your board sees is an average. Averages hide the cohorts quietly draining cash.
Day 2
The 3 backend triggers that stop retention decay
Most teams treat retention as a campaign problem. It's an infrastructure problem.
Day 3
Your Retention Debt score + the 90-Day Blueprint
A framework for scoring your own retention infrastructure — plus the full PDF with every playbook behind the results.
Includes PDFThe class has its own page. The Cohort Inversion Equation →
The revenue layer most teams ignore is the one that compounds.
Teardowns. Architectures. Operator-level findings.
SubscribeFree. Unsubscribe anytime.