Retention
The repeat-purchase flywheel
Acquisition is a treadmill; repeat purchases are a flywheel. A second order costs a fraction of the first, so a few points of repeat rate can transform the business.
If every sale must be bought with ad spend, you're on a treadmill that gets more expensive. Repeat purchases are the flywheel: existing customers cost far less to sell to and lift LTV, which raises your affordable CAC, which funds more acquisition. The skill is measuring repeat rate and pulling the few levers that move it. AI models the impact from your numbers; you run the levers.
The repeat-purchase flywheel
Buying every sale with ads is a treadmill; repeat purchases are a flywheel that spins faster the more it turns.
A second order costs a fraction of the first, lifts LTV, and raises the CAC you can afford, which funds more growth. AI models what a few points of repeat rate do to your economics; you supply the real numbers and run the levers, because the relationship work is yours.
Fastest path: one prompt, end to end
AI prompt — paste into ChatGPT / Claude
You are a retention strategist. Use MY numbers only (invent nothing). Current repeat-purchase rate: [%] AOV: [$] Contribution margin %: [%] CAC: [$] My category / typical reorder cycle: [e.g. consumable ~45 days / durable ~yearly] Do this: 1. Model the impact: if repeat rate rises by 5 and 10 points, what happens to 90-day LTV and my affordable CAC? Show the math from my numbers. 2. Rank the highest-leverage repeat levers for MY category (post-purchase flow, replenishment reminders timed to my cycle, loyalty, subscription, product-education). 3. Give the ONE lever to start with and why it fits my reorder cycle. 4. Name the metric to watch (repeat rate or 2nd-order rate) and a healthy direction. If a number is missing, ask; do not guess. Output: impact model + ranked levers + first move + metric to watch.
Or do it in 4 steps
- Measure your repeat rate honestly. What share of customers place a second order, and how long it takes. This one number tells you whether you have a flywheel or a treadmill, and most stores never look at it.
- Time your outreach to the reorder cycle. For consumables, a replenishment reminder just before they'd run out is the single biggest lever. For durables, cross-sell a complementary product instead. The right timing beats more emails.
- Make the second order easy and rewarded. A post-purchase flow (see post-purchase-experience), a one-tap reorder, a loyalty point or reorder code (see loyalty-programs), or a subscription for true consumables (see subscription-basics). Remove friction, add a small reason.
- Reinvest the compounding. As repeat rate rises, LTV rises, so your affordable CAC rises, so you can win more customers profitably. Track it as a loop, not a one-off, that's what makes it a flywheel instead of a tactic.
Worked example (labeled): 1,000 customers, AOV $50, 55% contribution ($27.50). At a 20% repeat rate, 200 second orders add $5,500 contribution at near-zero acquisition cost.
Lift repeat to 30% and it's 300 orders, $8,250, a 50% jump in repeat contribution with no extra ad spend. That gain also raises the CAC you can afford on new customers. Model your own repeat rate.
Track repeat rate monthly; a rising rate compounds, a falling one means you're back on the acquisition treadmill.
Do
- ✓Measure your repeat rate honestly: what share of customers place a second order, and how long it takes.
- ✓Time outreach to the reorder cycle: a replenishment reminder just before consumables run out is the single biggest lever.
- ✓Make the second order easy and rewarded: one-tap reorder, a loyalty point, or a subscription for true consumables.
- ✓Track repeat rate as a compounding loop, not a one-off, so rising LTV keeps raising the CAC you can afford.
Avoid
- ✕Don't keep buying every sale with ads while ignoring repeat rate; that's a treadmill that only gets more expensive.
- ✕Don't blast more emails when the fix is better timing; the reminder that lands just before a reorder beats ten generic sends.
- ✕Don't push replenishment on a durable that reorders yearly; cross-sell a complementary product instead.
- ✕Don't judge the flywheel on one month; a single reading can't tell you whether the loop is spinning up or slowing down.
Quick tips
- Model it before you act: a 5-point lift in repeat rate visibly changes 90-day LTV and the CAC you can afford; run the math on your own numbers.
- Pick one lever that fits your cycle and start there, rather than launching post-purchase flow, loyalty and subscription all at once.
- Watch second-order rate specifically; it's the earliest signal that the flywheel is catching.
Brand in focus
Dollar Shave Club — turning first orders into a subscription flywheel
DollarShaveClub.comAcquired by Unilever for a reported $1B, on a base largely built from recurring subscription orders
Dollar Shave Club fits because razors are a textbook consumable, and it built the whole business on the flywheel: a cheap, memorable first order converted into an automatic monthly refill, so a huge share of revenue came from repeat shipments instead of paid acquisition. What it did well was remove all friction from the second, third and fortieth order by defaulting to subscription. Watch-out: subscription only works when the product genuinely gets used up on a cycle; forcing it onto a durable just breeds cancellations.