Whenever you remove watermark from a campaign, you select a Start and End dates for it. Suppose you are going to offer a discount to your customers for a week or 15 days only on a future date. In this case, you can set a Start date and End dates keeping in mind the start and end dates of your discount offer. Now, the watermark text set by you will be visible before the Start date as well as after the End date is crossed. Which means that your campaign will be active only on the dates you have set and will expire after that.