Why is the countdown stopping after a while?

In order to provide a quick dowload, and to minimize its weight (KB), the Countdown timer content block generates an animated gif file that lasts 60 seconds, which gives the visitor enough time to see it in the email or landing page. The timer stops after this 60 seconds. When the email is re-opened, or the landing page re-visited, the time is reset to start for another 60 seconds, with the remaining time left.