About keyframes and effect duration
When you change the duration of an effect such as a filter or behavior in the Timeline track area, the timing of all keyframes applied to that effect is scaled proportionally. This means that keyframed changes to an effect speed up or slow down when the effect is shortened or lengthened. This happens whether you change the duration of the effect bar, or change the duration of the image bar an effect is applied to.
Object parameters such as Position, Rotation, Scale, Opacity, and so on are not affected.
Tip: To change the duration of a timebar without altering the timing of keyframes, hold down the Command key while dragging one end of the bar left or right.