That doesn't depend on the time, only on the number of frames:
"...a Flash movie can have up to 16000 frames." ("The magic number")

Here is a simple calculation:
16000(max. frames) / 30(fps) = 533 (sec)
If a slide is shown 4 sec and effect 1 sec then:
533 / (4+1) = 106 (slides)
So you can use either 106 slides with the fps=30 or more slides with less fps.