Put simply, each time we serve a user a banner and they do not click on it, the probability that we serve another banner decreases until ultimately the engine will stop serving them banners.
On average, we will serve 8-12 banners before we stop retargeting that user. We have reporting around this that we can pull for you. Most users get 1-3 banners and the number of users who see more is generally less.
What’s interesting is that users who see 13+ banners typically have the highest conversion rate. This tells us the engine is heavily targeting these users because they are highly engaged and continuously click/return to the site.