What you have, you don't want to lose.

What the research shows

Kahneman and Tversky's Prospect Theory established that people experience losses and gains asymmetrically. Losing €50 causes significantly more distress than finding €50 causes pleasure. The empirical ratio sits at roughly 2 to 1: losses loom about twice as large as equivalent gains.

Richard Thaler extended this in 1980 with the Endowment Effect: once we possess something — even mentally — we overvalue it. A half-full stamp card already belongs to the customer. Those stamps feel like theirs. The prospect of losing them activates loss aversion.

This is why a card with a reasonable expiry window motivates more strongly than a card with none. Not because it threatens — but because it gives the customer something to protect.

"Once an item is owned, it is valued more highly than before ownership." — Thaler (1980), Journal of Economic Behavior & Organization

Sources: Kahneman & Tversky (1979), "Prospect Theory: An Analysis of Decision under Risk", Econometrica 47(2), 263–291. Thaler (1980), "Toward a Positive Theory of Consumer Choice", Journal of Economic Behavior & Organization 1(1), 39–60.

What this means for your shop

The first customer has something to lose. Those 7 stamps represent time and money already invested. If the card expires, it's not just a missed gain — it feels like a real loss.

The second customer starts at zero. Nothing is at stake, no momentum pulling them forward — only the abstract idea that they could start someday. That's a weak motivator.

Expiry doesn't create new customers. But it gives existing customers a concrete reason to close the gap — before it's too late.

Finding the right window

Too short, and expiry feels like a trap. Customers feel cheated when stamps expire that they had no realistic chance of using. Too long, and the urgency disappears — nobody thinks about an expiry date that's a year away.

A practical guide by shop type:

A useful rule of thumb: think about how often a loyal regular visits per month. Multiply by 4 to 6. That's roughly the right expiry window.

How this works in Summa

In Summa, you can set a separate expiry window for each programme. The setting is called "Expiry after inactivity" and takes a value in days. Leave it blank and the card never expires.

A customer's card expires if they haven't collected any new stamps within that window. When a card expires, the customer is informed and can create a new card to start again.

Is this fair to customers?

That's a fair question. Here's the direct answer: an expiry window is fair when it's generous enough that engaged customers are never caught out. Customers who visit regularly will never lose stamps — their card stays alive through their normal pattern.

Expiry only affects customers who haven't visited in months. For them, an expired card isn't a loss — it's an invitation to start fresh. Many do. Those who don't would likely not have returned regardless.