In SlideShark, the default slide duration is 3 seconds. Thus, if a slide contains just a GIF animation, the animation will animate for 3 seconds.
To modify the length of time your GIF plays, follow these steps:
- Add a text box that contains only a space character on the PowerPoint slide
- Animate this new text box for the length of time you wish the GIF to play
- Set the animation timing to "with previous"