There are only two reasons why I ever have a slide longer than the default 3 seconds:
- If I stagger objects on the timeline to have them enter the slide at different times
- I there is slide audio, because in that case the slide duration has to be at least the duration of the audio clip.
You can control with an advanced or shared action (interaction is a widget in Captivate terminology) but I don't understand how you would use Effects for that kind of control?