Hi D
Confirmed.
Same behavior in VP7.0. The timeline is not pushed along if the duration of image 1 is increased. (Try 5 seconds > 10 seconds...Image 2 disappears) I have reported this as a possible bug. The durations can be also altered in Storyboard mode and are seen correctly here following one another with the entered values, but switching back to timeline mode the second image is still covered up!
Nat