For Facebook it is important that their users do not find the ads on the site annoying or offensive and they strive to show ads that the users like and want to interact with. Therefore, when users stop clicking your ad, your impressions will start decreasing. But do not despair! There is a solution. By continuously refreshing your images and ad copy you can avoid ad fatigue.
To make sure that your campaigns do not come to a halt it is important to always have fresh ads in store that you can activate when your impressions start decreasing.
It can be helpful to make a plan of what ads to activate at what time. I doing so, you avoid the risk of forgetting to refresh your ads before peak-seasons and other important dates.