Replenishment emails: the lifecycle flow that buys itself

Replenishment applies to consumable products: coffee, skincare, pet food, vitamins, contact lenses, household supplies. Purchase cycle is predictable — buy, use, run out, buy again. The email catches users at the "run out" moment.

Revenue per send in replenishment is typically 5–15× marketing broadcast because the intent is already there. The email's job is closing the gap between "user is running out" and "user notices they're running out and remembers where to buy". That's a smaller gap than any other lifecycle trigger closes, which is why the revenue per send is so high.

Message 1: Anticipated depletion reminder. Timing: 5–7 days before the user's typical re-order window, calculated from purchase history. Subject: "Running low on [product]?" Content: one-click re-order of the same product, estimated delivery date, link to adjust quantity or subscription if relevant.

Message 2: "You might be out by now" nudge. Timing: 10 days after message 1 if no re-order. Subject: "Time to restock [product]". Content: re-order CTA, subtle urgency, alternative sizes if relevant. Catches users who meant to re-order and forgot — a non-trivial share.

Message 3 (optional): Subscription nudge. Timing: 30 days after original purchase if still no re-order. Subject: "Never run out — set up auto-delivery". Content: subscription pitch with discount, explaining the convenience. Converts one-time buyers into subscribers. Lower conversion than messages 1 and 2, but higher LTV impact when it lands.

"Anticipated depletion" date is the hardest part. Three approaches, simple to sophisticated:

Category default. Every product has a default depletion window — coffee 30 days, skincare moisturiser 45 days, 5kg dog food 60 days. Use the category default unless you have user-specific data. Simple, fast to ship, acceptably accurate for most products.

Per-user average. For a user who's re-ordered multiple times, use their own average re-order interval. Someone who reliably re-orders coffee every 21 days gets message 1 on day 15. More accurate for returning customers. Requires historical data.

Product-plus-size-plus-household. Someone who buys the 1kg bag depletes faster than someone who buys 5kg. A household-size signal (from signup data or past purchases) refines further. Lifts accuracy 20–30% over category default but requires attribute data most programs don't have cleanly.

Start with category default. Move to per-user average once you have six-plus months of repurchase data. Only build the size/household model if the revenue justifies the engineering. Most programs don't need to, and most programs that do it anyway don't measure the actual lift.

Replenishment email is fundamentally a workaround for users who haven't subscribed yet. Long-term play is subscription — auto-ship at the predicted interval, clear path to pause or cancel.

Treat replenishment as subscription-funnel touches, not just one-off reminders. Every replenishment email should have a subtle "or set up auto-delivery and skip the reminders" option. Path from one-time buyer → replenishment responder → subscriber is the LTV compound that makes consumable businesses actually work.

Measure subscription conversion from replenishment separately from one-time re-order conversion. A 10% subscription conversion is worth 3× more LTV than a 30% one-time re-order.

Why not push everyone to subscription from day one? Subscription has higher commitment cost for the user. Many first-time buyers aren't ready. Replenishment bridges the commitment gap — get them through a second and third one-time purchase, then convert when the product is clearly part of their routine. Pushing subscription too early actually suppresses first-purchase conversion, which is the worst of both worlds.

Re-order rate in next 14 days (holdout test): with replenishment sent vs suppressed holdout. Expected incremental lift: 15–30% on 14-day re-order rate for consumable categories.

Time-to-reorder: median days from previous purchase to next. Replenishment should shorten this by 5–10 days. Reminded users re-order sooner.

Subscription conversion from replenishment: percent of message recipients who set up auto-delivery. 2–8% is healthy. Below 1% means the subscription CTA isn't being noticed — usually because it's buried at the bottom of message three.

Revenue per replenishment send: typically $2–$10 per send for consumer consumables, vs $0.10–$0.50 for marketing broadcast. Order-of-magnitude difference is why programs that ship replenishment often see it as their largest lifecycle revenue line.

Some practical edge cases: if a user buys multiple consumables, run replenishment per-product, not per-user. Coffee buyer who also bought filters gets two parallel flows with different schedules. Cap combined frequency (no more than two replenishment messages per week per user) to avoid flooding high-LTV customers.

For non-consumables, replenishment works less directly. Closest analogue for durable goods is an "accessory or refill" prompt — camera owners buy SD cards, printer buyers need toner. Weaker signal than consumable depletion (timing less predictable, correlation weaker), but the structural play is the same.

For cancellation saves: the pattern is similar but the trigger is different. User about to cancel gets a "before you cancel" email. User who just cancelled gets a "we'll miss you + here's how to resume" email. These are cancellation-save flows and belong in their own sequence, not blended with replenishment.

places replenishment almost always first or second for programs with repeat-purchase consumable products. It's the flow with the clearest line from "user behaviour" to "revenue per send" and the rare flow where the ROI math is obvious inside the first month.